Updated on 2024/03/15

写真a

 
Takahiro Moriyama
 
Organization
Graduate School of Engineering Materials Physics 1 Professor
Graduate School
Graduate School of Engineering
Undergraduate School
School of Engineering Physical Science and Engineering
Title
Professor

Degree 3

  1. Ph.D. (Physics) ( 2008.8   University of Delware ) 

  2. M. Eng. ( 2003.3   Tohoku University ) 

  3. B.S. ( 2001.3   Tohoku University ) 

Research Interests 6

  1. THz spintronics

  2. Spintronics

  3. Antiferromagnets

  4. Magnetism

  5. Magneto-optics

  6. High frequency measurements

Research Areas 2

  1. Nanotechnology/Materials / Applied physical properties  / spintronics

  2. Natural Science / Magnetism, superconductivity and strongly correlated systems  / magnetism

Research History 6

  1. Nagoya University   Graduate School of Engineering Materials Physics   Professor

    2023.4

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    Country:Japan

  2. Kyoto University   Institute for Chemical Research   Associate professor

    2016.4 - 2023.3

  3. National Institute for Standards and Technology (USA)   Guest Researcher

    2014.9 - 2014.12

  4. Kyoto University   Institute for Chemical Research   Assistant Professor

    2012.8 - 2016.3

  5. TDK-Headway Technologies,Inc. (USA)   R&D   Sr. Characterization Engineer

    2011.11 - 2012.8

  6. Cornell University (USA)   Physics & Applied Physics   Postdoctoral Associate

    2008.8 - 2011.11

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Education 3

  1. University of Delaware   Art and Science   Department of Physics, Ph.D.

    2003.9 - 2008.8

  2. Tohoku University   Graduate school of Engineering   Materials Science, M. Eng.

    2001.4 - 2003.3

  3. Tohoku University   Engineering department   Materials Science, B.S.

    1997.4 - 2001.3

Professional Memberships 3

  1. American Physical Society

  2. THE JAPAN SOCIETY OF APPLIED PHYSICS

  3. THE MAGNETICS SOCIETY OF JAPAN

Committee Memberships 8

  1. IEEE magnetic society   Advisory Comittee Member  

    2022.12 - 2025.12   

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    Committee type:Academic society

  2. The Japan Society of Appiled Physics, Spintronics division   General Comittee Member  

    2021.3   

  3. The Japan Society of Appiled Physics   Secretary  

    2019.3   

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    Committee type:Academic society

  4. The Japan Society of Appiled Physics, Spintronics division   Secretary  

    2019.3 - 2021.2   

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    Committee type:Academic society

  5. New Journal of Physics   Editorial board member  

    2018.3   

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    Committee type:Academic society

  6. New Journal of Physics   Editorial board member  

    2018.3   

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    Committee type:Other

  7. 応用物理学会スピントロニクス研究会   企画幹事  

    2017.9 - 2019.3   

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    Committee type:Academic society

  8. The Japan Society of Applied Physics, spintronics division   Organizing comittee  

    2017.9 - 2019.3   

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    Committee type:Academic society

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Awards 3

  1. Contribution Award

    2020.9   The magnetic society of Japan   Contribution to the 43rd annual conference in magnetics in Japan

  2. Best Papar Award

    The magnetic society of Japan   Magnetoresistance in Bilayer of Heavy Metal and Non-collinear Antiferromagnet

    Takahiro Moriyama

  3. Scholastic Excellence Named In Dean's List

    University of Delaware  

    Takahiro Moriyama

 

Papers 181

  1. Ultrafast spin-to-charge conversion in antiferromagnetic (111)-oriented L12-Mn3Ir

    Huiling Mao, Yuta Sasaki, Yuta Kobayashi, Shinji Isogami, Teruo Ono, Takahiro Moriyama, Yukiko K. Takahashi, Kihiro T. Yamada

    Applied Physics Letters   Vol. 123 ( 21 )   2023.11

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    Publishing type:Research paper (scientific journal)  

    DOI: 10.1063/5.0168138

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  2. Spin Hall magnetoresistive detection of easy-plane magnetic order in the van der Waals antiferromagnet NiPS3

    Kohki Sugi, Takuto Ishikawa, Motoi Kimata, Yoichi Shiota, Teruo Ono, Takeo Kato, Takahiro Moriyama

    Physical Review B   Vol. 108 ( 6 )   2023.8

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    Publishing type:Research paper (scientific journal)  

    DOI: 10.1103/PhysRevB.108.064434

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  3. Direct observation of antiferromagnetic domains and field-induced reversal in Pt/Cr2O3/Pt epitaxial trilayers

    Kakeru Ujimoto, Hiroki Sameshima, Kentaro Toyoki, Yoshinori Kotani, Takahiro Moriyama, Kohji Nakamura, Ryoichi Nakatani, Yu Shiratsuchi

    Applied Physics Letters   Vol. 123 ( 2 )   2023.7

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    Publishing type:Research paper (scientific journal)   Publisher:AIP Publishing  

    Antiferromagnet does not show the net magnetization, whereas the finite uncompensated moment can residue at the surface. On the surface of the magnetoelectric antiferromagnet, the finite boundary magnetization can acquire the magnetic response. In this paper, we address the magnetic response of the boundary magnetization in the Pt/magnetoelectric Cr2O3/Pt epitaxial trilayer based on the anomalous Hall effect (AHE) and the soft x-ray magnetic circular dichroism (XMCD). Decreasing the Cr2O3 thickness down to 15 nm, the film acquired the magnetic responsiveness, which manifested as the rectangular hysteresis in the magnetic field dependence of the AHE. The sizable XMCD intensity and the rectangular magnetic field dependence of the XMCD intensity revealed that the magnetic response was attributed to the interfacial Cr moment. The detailed investigation of AHE and XMCD revealed that the domain wall motion dominated the reversal process of the boundary magnetization, which was directly visualized by the scanning XMCD microscope.

    DOI: 10.1063/5.0156254

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  4. Micromagnetic understanding of evolutions of antiferromagnetic domains in NiO

    Takahiro Moriyama, Luis Sánchez-Tejerina, Kent Oda, Takuo Ohkochi, Motoi Kimata, Yoichi Shiota, Hiroyuki Nojiri, Giovanni Finocchio, Teruo Ono

    Physical Review Materials   Vol. 7 ( 5 )   2023.5

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    Publishing type:Research paper (scientific journal)   Publisher:American Physical Society (APS)  

    DOI: 10.1103/PhysRevMaterials.7.054401

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    Other Link: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevMaterials.7.054401/fulltext

  5. Observation of mode splitting by magnon–magnon coupling in synthetic antiferromagnets

    Daiju Hayashi, Yoichi Shiota, Mio Ishibashi, Ryusuke Hisatomi, Takahiro Moriyama, Teruo Ono

    Applied Physics Express   Vol. 16 ( 5 )   2023.5

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    Publishing type:Research paper (scientific journal)  

    DOI: 10.35848/1882-0786/acd5a6

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  6. Quantitative optical imaging method for surface acoustic waves using optical path modulation

    Takahiro Moriyama

    Physical Review B   Vol. 107 ( 16 )   2023.4

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    Publishing type:Research paper (scientific journal)  

    DOI: 10.1103/PHYSREVB.107.165416

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  7. Generation of third-harmonic spin oscillation from strong spin precession induced by terahertz magnetic near fields

    Zhenya Zhang, Fumiya Sekiguchi, Takahiro Moriyama, Shunsuke C. Furuya, Masahiro Sato, Takuya Satoh, Yu Mukai, Koichiro Tanaka, Takafumi Yamamoto, Hiroshi Kageyama, Yoshihiko Kanemitsu, Hideki Hirori

    Nature Communications   Vol. 14 ( 1 )   2023.3

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    Publishing type:Research paper (scientific journal)   Publisher:Springer Science and Business Media LLC  

    Abstract

    The ability to drive a spin system to state far from the equilibrium is indispensable for investigating spin structures of antiferromagnets and their functional nonlinearities for spintronics. While optical methods have been considered for spin excitation, terahertz (THz) pulses appear to be a more convenient means of direct spin excitation without requiring coupling between spins and orbitals or phonons. However, room-temperature responses are usually limited to small deviations from the equilibrium state because of the relatively weak THz magnetic fields in common approaches. Here, we studied the magnetization dynamics in a HoFeO<sub>3</sub> crystal at room temperature. A custom-made spiral-shaped microstructure was used to locally generate a strong multicycle THz magnetic near field perpendicular to the crystal surface; the maximum magnetic field amplitude of about 2 T was achieved. The observed time-resolved change in the Faraday ellipticity clearly showed second- and third-order harmonics of the magnetization oscillation and an asymmetric oscillation behaviour. Not only the ferromagnetic vector M but also the antiferromagnetic vector L plays an important role in the nonlinear dynamics of spin systems far from equilibrium.

    DOI: 10.1038/s41467-023-37473-1

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    Other Link: https://www.nature.com/articles/s41467-023-37473-1

  8. Pulse-width dependence of spin–orbit torque switching in Mn<sub>3</sub>Sn/Pt thin films

    Yuta Kobayashi, Yoichi Shiota, Hideki Narita, Teruo Ono, Takahiro Moriyama

    Applied Physics Letters   Vol. 122 ( 12 ) page: 122405 - 122405   2023.3

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    Publishing type:Research paper (scientific journal)   Publisher:AIP Publishing  

    Spin–orbit torque (SOT) switching in chiral antiferromagnets, such as D0<sub>19</sub>-Mn<sub>3</sub>Sn, has opened prospects in antiferromagnetic spintronics. In this paper, we investigated the critical switching voltage as a function of the voltage pulse width in order to explore the thermal stability factor Δ in the D0<sub>19</sub>-Mn<sub>3</sub>Sn. Although the critical switching voltage is found to decrease with increasing the voltage pulse width as expected by the thermally activated switching process with Δ of 131.1 at 300 K, our detailed examinations reveal that the Joule heating due to the voltage pulse could induce the magnetic phase transition in the D0<sub>19</sub>-Mn<sub>3</sub>Sn, which significantly alters the energy landscape relevant to the SOT switching. This assisting mechanism for the SOT switching inhibits an accurate determination of Δ but could deliver a smaller Δ than the actual. Our study provides cautionary note in estimating the thermal stability of the chiral antiferromagnets.

    DOI: 10.1063/5.0144602

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  9. Electrical Detection of Antiferromagnetic Dynamics in Gd - Co Thin Films Using 154-GHz Gyrotron Irradiation

    S. Funada, Y. Ishikawa, M. Kimata, K. Hayashi, T. Sano, K. Sugi, Y. Fujii, S. Mitsudo, Y. Shiota, T. Ono, T. Moriyama

    Physical Review Applied   Vol. 19 ( 3 )   2023.3

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    Publishing type:Research paper (scientific journal)   Publisher:American Physical Society (APS)  

    DOI: 10.1103/physrevapplied.19.l031003

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    Other Link: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevApplied.19.L031003/fulltext

  10. Rectification Effect of Non-Centrosymmetric Nb/V/Ta Superconductor

    R. Kawarazaki, R. Iijima, H. Narita, R. Hisatomi, Y. Shiota, T. Moriyama, T. Ono

    Journal of the Magnetics Society of Japan   Vol. 47 ( 5 ) page: 133 - 136   2023

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:The Magnetics Society of Japan  

    <p>  The superconducting diode effect in which electrical resistance is zero in only one direction has recently been reported in superconductors without inversion symmetry. Previous studies investigated the nonreciprocity of the critical current, but little has been known about the rectification effect when AC currents are applied. Herein, we examined the rectification characteristics of a non-centrosymmetric Nb/V/Ta artificial superlattice under AC currents. The rectification strength can be modulated by an applied magnetic field, and its polarity can be tuned by the magnetic field. Furthermore, we find that the magnetic field dependence of the rectification is different from that of the nonreciprocal critical current.</p>

    DOI: 10.3379/msjmag.2309r001

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    CiNii Research

  11. Magnetic-field-induced polarity oscillation of superconducting diode effect

    Takahiro Moriyama

    Applied Physics Express   Vol. 15 ( 11 )   2022.11

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    Publishing type:Research paper (scientific journal)  

    DOI: 10.35848/1882-0786/AC99B9

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  12. Electric field effect on spectroscopic g-factor and magnetic anisotropy in a Pt/Co/MgO ultrathin film

    Takahiro Moriyama

    Japanese Journal of Applied Physics   Vol. 61 ( 10 )   2022.10

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    Publishing type:Research paper (scientific journal)   Publisher:{IOP} Publishing  

    DOI: 10.35848/1347-4065/AC9025

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  13. Low ferrimagnetic damping in Gd3Fe5O12 epitaxial films grown using pulsed laser deposition

    S. Funada, D. Kan, K. Kuwano, Y. Shiota, R. Hisatomi, T. Moriyama, Y. Shimakawa, T. Ono

    Applied Physics Letters   Vol. 121 ( 9 )   2022.8

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    Publishing type:Research paper (scientific journal)  

    DOI: 10.1063/5.0099618

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  14. Extrinsic contribution to anomalous Hall effect in chiral antiferromagnetic (111)-oriented L1<sub>2</sub>-Mn<sub>3</sub>Ir films

    Yuta Kobayashi, Motoi Kimata, Daisuke Kan, Tetsuya Ikebuchi, Yoichi Shiota, Hiroshi Kohno, Yuichi Shimakawa, Teruo Ono, Takahiro Moriyama

    Japanese Journal of Applied Physics   Vol. 61 ( 7 ) page: 070912 - 070912   2022.7

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    Publishing type:Research paper (scientific journal)   Publisher:IOP Publishing  

    Abstract

    Chiral antiferromagnets are regarded as a new class of antiferromagnets owing to its intriguing spin transport properties such as a sizable anomalous Hall effect (AHE). In this work, we fabricated chiral antiferromagnetic L1<sub>2</sub>-Mn<sub>3</sub>Ir (111)-oriented films and investigated the anomalous Hall conductivity with respect to the chemical order parameter $S.$ It is found that the anomalous Hall conductivity in (111)-oriented films is much more pronounced compared to (001)-oriented films, which is consistent with the theoretical prediction. We also found that the anomalous Hall conductivity strongly depends on the longitudinal conductivity, which could suggest an extrinsic contribution to the AHE in L1<sub>2</sub>-Mn<sub>3</sub>Ir.

    DOI: 10.35848/1347-4065/ac7625

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    Other Link: https://iopscience.iop.org/article/10.35848/1347-4065/ac7625/pdf

  15. Field-free superconducting diode effect in noncentrosymmetric superconductor/ferromagnet multilayers

    Hideki Narita, Jun Ishizuka, Ryo Kawarazaki, Daisuke Kan, Yoichi Shiota, Takahiro Moriyama, Yuichi Shimakawa, Alexey V. Ognev, Alexander S. Samardak, Youichi Yanase, Teruo Ono

    Nature Nanotechnology   Vol. 17 ( 8 ) page: 823 - 828   2022.6

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    Publishing type:Research paper (scientific journal)   Publisher:Springer Science and Business Media LLC  

    DOI: 10.1038/s41565-022-01159-4

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    Other Link: https://www.nature.com/articles/s41565-022-01159-4

  16. Triaxial magnetic anisotropy and Morin transition in α-Fe2O3 epitaxial films characterized by spin Hall magnetoresistance

    Daisuke Kan, Takahiro Moriyama, Ryotaro Aso, Shinji Horai, Yuichi Shimakawa

    Applied Physics Letters   Vol. 120 ( 11 )   2022.3

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    Publishing type:Research paper (scientific journal)  

    DOI: 10.1063/5.0087643

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  17. Crystal orientation dependence of spin Hall angle in epitaxial Pt/FeNi systems

    Tetsuya Ikebuchi, Yoichi Shiota, Teruo Ono, Kohji Nakamura, Takahiro Moriyama

    Applied Physics Letters   Vol. 120 ( 7 )   2022.2

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    Publishing type:Research paper (scientific journal)  

    DOI: 10.1063/5.0078688

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  18. Temperature dependence of domain wall creep motion in ferrimagnetic Tb/CoFeB/MgO microwires

    Shiota, Y., Noda, K., Hirata, Y., Kuwano, K., Funada, S., Hisatomi, R., Moriyama, T., Stebliy, M., Ognev, A.V., Samardak, A.S., Ono, T.

    Journal of Magnetism and Magnetic Materials   Vol. 553   2022

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    Publishing type:Research paper (scientific journal)  

    DOI: 10.1016/j.jmmm.2022.169251

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  19. Polarization-Selective Excitation of Antiferromagnetic Resonance in Perpendicularly Magnetized Synthetic Antiferromagnets

    Takahiro Moriyama

    Physical Review Applied   Vol. 18 ( 1 )   2022

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    Publishing type:Research paper (scientific journal)  

    DOI: 10.1103/PHYSREVAPPLIED.18.014032

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  20. Bismuth composition, thickness, and annealing temperature dependence of the spin Seebeck voltage in Bi-YIG films prepared using sol–gel solution and spin-coating method

    Yamamoto, M., Masaki, S., Shiota, Y., Moriyama, T., Kato, T., Ono, T., Shima, M., Yamada, K.

    Journal of Magnetism and Magnetic Materials   Vol. 556   page: 169416 - 169416   2022

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    Publishing type:Research paper (scientific journal)   Publisher:Elsevier BV  

    DOI: 10.1016/j.jmmm.2022.169416

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  21. Long-distance spin current transmission in single-crystalline NiO thin films

    Tetsuya Ikebuchi, Yuta Kobayashi, Itaru Sugiura, Yoichi Shiota, Teruo Ono, Takahiro Moriyama

    Applied Physics Express   Vol. 14 ( 12 )   2021.12

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    Publishing type:Research paper (scientific journal)   Publisher:{IOP} Publishing  

    DOI: 10.35848/1882-0786/ac3575

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  22. Inhomogeneous magnetic properties characterized by simultaneous electrical and optical detection of spin-torque ferromagnetic resonance

    Yoichi Shiota, Ryusuke Hisatomi, Takahiro Moriyama, Alexander S. Samardak, Teruo Ono

    Applied Physics Letters   Vol. 119 ( 19 )   2021.11

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    Publishing type:Research paper (scientific journal)  

    DOI: 10.1063/5.0070012

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  23. Change of longitudinal spin Seebeck voltage with annealing in Y3Fe5O12 films formed by densely packed nanocrystals

    Keisuke Yamada, Shinya Masaki, Mikiya Yamamoto, Keita Kondo, Yuichiro Kurokawa, Yoichi Shiota, Takahiro Moriyama, Teruo Ono, Hiromi Yuasa, Mutsuhiro Shima

    Journal of Magnetism and Magnetic Materials   Vol. 535   page: 168093 - 168093   2021.10

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    Publishing type:Research paper (scientific journal)   Publisher:Elsevier BV  

    DOI: 10.1016/j.jmmm.2021.168093

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  24. Positive correlation between interlayer exchange coupling and the driving current of domain wall motion in a synthetic antiferromagnet

    Yu Min Hung, Yoichi Shiota, Shogo Yamada, Minoru Ohta, Tatsuo Shibata, Tomoyuki Sasaki, Ryusuke Hisatomi, Takahiro Moriyama, Teruo Ono

    Applied Physics Letters   Vol. 119 ( 3 ) page: 032407 - 032407   2021.7

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    Publishing type:Research paper (scientific journal)   Publisher:AIP Publishing  

    DOI: 10.1063/5.0056056

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  25. Control of antiferromagnetic resonance and the Morin temperature in cation doped α-Fe2-xMxO3 (M = Al, Ru, Rh, and In)

    Kensuke Hayashi, Keisuke Yamada, Mutsuhiro Shima, Yutaka Ohya, Teruo Ono, Takahiro Moriyama

    Applied Physics Letters   Vol. 119 ( 3 )   2021.7

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    Antiferromagnets are one of the few candidate materials that can work at THz frequency and are, therefore, a potential material for THz technology recently attracting interest from high-speed communication and sensing applications. In this work, we investigate an antiferromagnetic resonant frequency (ωr) tunability for cation doped α-Fe2O3. It is found that, with various cation dopants (Al, Ru, Rh, and In), the resonant frequency can be tuned in a range between a millimeter-wave band and a THz band. We also complementally discuss the mechanism of the Morin temperature (TM) shift upon cation doping by the temperature and dopant dependence of ωr. A good frequency tunability shown in this work suggests that cation doped α-Fe2O3 is a useful material for millimeter-wave and THz applications.

    DOI: 10.1063/5.0053586

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  26. Observation of nonreciprocal superconducting critical field

    Yuta Miyasaka, Ryo Kawarazaki, Hideki Narita, Fuyuki Ando, Yuhei Ikeda, Ryusuke Hisatomi, Akito Daido, Yoichi Shiota, Takahiro Moriyama, Youichi Yanase, Teruo Ono

    Applied Physics Express   Vol. 14 ( 7 )   2021.7

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:{IOP} Publishing  

    We report that the superconducting critical magnetic field can be nonreciprocal under a bias of an electric current in a superconducting [Nb/V/Ta]( n ) superlattice without a center of inversion. The critical magnetic field showed a clear difference between positive and negative magnetic fields. Furthermore, the magnitude relation between the positive and negative critical magnetic fields is reversed when the direction of the electric current is reversed. Our findings indicate that the superconducting gap can be anisotropic by the application of an electric current.

    DOI: 10.35848/1882-0786/ac03c0

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  27. Estimation of Magnetic Domain Size in Chiral Antiferromagnet Mn<sub>3</sub>Ir by the Anomalous Hall Measurements

    Y. Kobayashi, T. Ikebuchi, Y. Shiota, T. Ono, T. Moriyama

    Journal of the Magnetics Society of Japan   Vol. 45 ( 4 ) page: 75 - 78   2021.7

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    Publishing type:Research paper (scientific journal)   Publisher:The Magnetics Society of Japan  

    DOI: 10.3379/msjmag.2107l002

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  28. Investigation of the upper critical field in artificially engineered Nb/V/Ta superlattices

    Fuyuki Ando, Ryo Kawarazaki, Masahiro Naritsuka, Yuichi Kasahara, Yuta Miyasaka, Hideki Narita, Daisuke Kan, Yoichi Shiota, Takahiro Moriyama, Yuichi Shimakawa, Yuji Matsuda, Teruo Ono

    Japanese Journal of Applied Physics   Vol. 60 ( 6 ) page: 060902 - 060902   2021.6

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    Publishing type:Research paper (scientific journal)   Publisher:{IOP} Publishing  

    DOI: 10.35848/1347-4065/abfdc1

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    Other Link: https://iopscience.iop.org/article/10.35848/1347-4065/abfdc1/pdf

  29. The 2021 Magnonics Roadmap

    A Barman, Gianluca Gubbiotti, Sam Ladak, Adekunle Olusola Adeyeye, Maciej Krawczyk, Joachim Gräfe, Christoph Adelmann, Sorin Cotofana, Azad Naeemi, Vitaliy I Vasyuchka, Burkard Hillebrands, S A Nikitov, Haiming Yu, Dirk Grundler, Alexandr Sadovnikov, Andrew A. Grachev, S. E. Sheshukova, Jean-Yves Duquesne, Massimiliano Marangolo, Csaba Gyorgy, Wolfgang Porod, V E Demidov, Sergei Urazhdin, Sergej Demokritov, Edoardo Albisetti, Daniela Petti, Riccardo Bertacco, Helmut Schulteiss, Volodymyr V Kruglyak, Vlad D Poimanov, Ashok Kumar Sahoo, Jaivardhan Sinha, Hyunsoo Yang, Markus Muenzenberg, Takahiro Moriyama, Shigemi Mizukami, Pedro Landeros, Rodolfo Andrés Gallardo, Giovanni Carlotti, Joo-Von Kim, Robert L Stamps, Robert E Camley, Bivas Rana, Y Otani, Weichao Yu, Tao Yu, Gerrit E. W. Bauer, Christian H Back, Goetz S Uhrig, Oleksandr V Dobrovolskiy, Sebastiaan van Dijken, Barbora Budinska, Huajun Qin, Andrii Chumak, Aleksandr Khitun, Dmitri E. Nikonov, Ian A Young, Benjamin Zingsem, Michael Winklhofer

    Journal of Physics: Condensed Matter   Vol. 33 ( 41 )   2021.3

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    Publishing type:Research paper (scientific journal)   Publisher:IOP Publishing  

    DOI: 10.1088/1361-648x/abec1a

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    Other Link: https://iopscience.iop.org/article/10.1088/1361-648X/abec1a/pdf

  30. Spin Wave Resonance in Perpendicularly Magnetized Synthetic Antiferromagnets

    M. Ishibashi, Y. Shiota, S. Funada, T. Moriyama, T. Ono

    Journal of the Magnetics Society of Japan   Vol. 45 ( 2 ) page: 25 - 29   2021.3

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    Publishing type:Research paper (scientific journal)   Publisher:The Magnetics Society of Japan  

    DOI: 10.3379/msjmag.2103r004

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  31. High thermal stability and low driven current achieved by vertical domain wall motion memory with artificial ferromagnet

    Yu Min Hung, Yoichi Shiota, Ryusuke Hisatomi, Takahiro Moriyama, Teruo Ono

    Applied Physics Express   Vol. 14 ( 2 ) page: 023001 - 023001   2021.2

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    Publishing type:Research paper (scientific journal)   Publisher:{IOP} Publishing  

    DOI: 10.35848/1882-0786/abd86a

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    Other Link: https://iopscience.iop.org/article/10.35848/1882-0786/abd86a/pdf

  32. Field-driven domain wall creep motion in ferrimagnetic Tb/CoFeB/MgO microwires

    Yuushou Hirata, Kaoru Noda, Yoichi Shiota, Takahiro Moriyama, Teruo Ono

    Japanese Journal of Applied Physics   Vol. 60 ( 2 ) page: 020902 - 020902   2021.2

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    Publishing type:Research paper (scientific journal)   Publisher:{IOP} Publishing  

    DOI: 10.35848/1347-4065/abd67d

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    Other Link: https://iopscience.iop.org/article/10.35848/1347-4065/abd67d/pdf

  33. Low Current Driven Vertical Domain Wall Motion Memory with an Artificial Ferromagnet

    Y. M. Hung, T. Li, R. Hisatomi, Y. Shiota, T. Moriyama, T. Ono

    Journal of the Magnetics Society of Japan   Vol. 45 ( 1 ) page: 6 - 11   2021.1

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    Publishing type:Research paper (scientific journal)   Publisher:The Magnetics Society of Japan  

    DOI: 10.3379/msjmag.2011r002

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  34. Estimation of Angular Momentum Compensation Temperature in GdFe Film by Magnetic Compton Scattering

    T. Ikebuchi, Y. Hirata, S. Funada, A. Tsukamoto, H. Ito, K. Suzuki, K. Hoshi, N. Tsuji, H. Sakurai, Y. Shiota, T. Moriyama, T. Ono

    Journal of the Magnetics Society of Japan   Vol. 45 ( 1 ) page: 1 - 5   2021.1

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    Publishing type:Research paper (scientific journal)   Publisher:The Magnetics Society of Japan  

    DOI: 10.3379/msjmag.2101l002

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  35. Tracheal Varicose Veins Associated with Klippel-Trenaunay Syndrome

    Takahiro Moriyama

    Anesthesiology     2021

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    Publishing type:Research paper (scientific journal)  

    DOI: 10.1097/ALN.0000000000004016

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  36. Observation of the dispersion relations for quantized coherent spin waves excited by a microwave antenna

    Yoichi Shiota, Ryusuke Hisatomi, Takahiro Moriyama, Teruo Ono

    Physical Review B   Vol. 102 ( 21 )   2020.12

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER PHYSICAL SOC  

    The propagation of coherent spin waves in permalloy microstrips was investigated using a heterodynemagneto-optical Kerr effect technique. The two-dimensional imaging reveals the mode interference with a high-order spin-wave mode along the microstrip width. The spin-wave dispersion relations across the microstrip width were deduced from fast Fourier transformations on the complex spin-wave amplitude of the one-dimensional scan, and multiple spin-wave modes were observed at the edges of the microstrips. These experimental results provide direct evidence for the quantization of spin-wave dispersion due to the finite width of the microstrips and enables us to evaluate the attenuation length for each quantized spin-wave mode.

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  37. Laser stimulated THz emission from Pt/CoO/FeCoB

    Yuta Sasaki, Guanqiao Li, Takahiro Moriyama, Teruo Ono, Rostislav V. Mikhaylovskiy, Alexey V. Kimel, Shigemi Mizukami

    Applied Physics Letters   Vol. 117 ( 19 ) page: 192403 - 192403   2020.11

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    DOI: 10.1063/5.0020020

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  38. Chromatic Aberration Effect in Refraction of Spin Waves

    T. Li, T. Taniguchi, Y. Shiota, T. Moriyama, T. Ono

    Journal of the Magnetics Society of Japan   Vol. 44 ( 6 ) page: 133 - 136   2020.11

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    DOI: 10.3379/msjmag.2011l003

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  39. Dependence of Gilbert damping constant on microstructure in nanocrystalline YIG coatings prepared by co-precipitation and spin-coating on a Si substrate Reviewed

    Keisuke Yamada, Kazuma Kogiso, Yoichi Shiota, Mikiya Yamamoto, Akinobu Yamaguchi, Takahiro Moriyama, Teruo Ono, Mutsuhiro Shima

    Journal of Magnetism and Magnetic Materials   Vol. 513   page: 167253 - 167253   2020.11

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    DOI: 10.1016/j.jmmm.2020.167253

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  40. Observation of superconducting diode effect Reviewed

    Fuyuki Ando, Yuta Miyasaka, Tian Li, Jun Ishizuka, Tomonori Arakawa, Yoichi Shiota, Takahiro Moriyama, Youichi Yanase, Teruo Ono

    Nature   Vol. 584 ( 7821 ) page: 373 - 376   2020.8

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    DOI: 10.1038/s41586-020-2590-4

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  41. Spin-orbit precession effect in a Py/Pt/Co tri-layer structure detected by ferromagnetic resonance Reviewed

    Yuki Hibino, Takahiro Moriyama, Kento Hasegawa, Tomohiro Koyama, Teruo Ono, Daichi Chiba

    Applied Physics Express   Vol. 13 ( 8 ) page: 083001 - 083001   2020.8

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    DOI: 10.35848/1882-0786/aba0dc

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  42. Spin–orbit torque based physical unclonable function Reviewed

    G. Finocchio, T. Moriyama, R. De Rose, G. Siracusano, M. Lanuzza, V. Puliafito, S. Chiappini, F. Crupi, Z. Zeng, T. Ono, M. Carpentieri

    Journal of Applied Physics   Vol. 128 ( 3 )   2020.7

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    This paper introduces the concept of spin-orbit-torque-magnetic random access memory (SOT-MRAM) based physical unclonable function (PUF). The secret of the PUF is stored into a random state of a matrix of perpendicular SOT-MRAMs. Here, we show experimentally and with micromagnetic simulations that this random state is driven by the intrinsic nonlinear dynamics of the free layer of the memory excited by the SOT. In detail, a large enough current drives the magnetization along an in-plane direction. Once the current is removed, the in-plane magnetic state becomes unstable evolving toward one of the two perpendicular stable configurations randomly. In addition, we propose a hybrid CMOS/spintronics model to simulate a PUF realized by an array of 16 × 16 SOT-MRAM cells and evaluate the electrical characteristics. Hardware authentication based on this PUF scheme has several characteristics, such as CMOS-compatibility, non-volatility (no power consumption in standby mode), reconfigurability (the secret can be reprogrammed), and scalability, which can move a step forward the design of spintronic devices for application in security.

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  43. Tailoring THz antiferromagnetic resonance of NiO by cation substitution Reviewed

    Takahiro Moriyama, Kensuke Hayashi, Keisuke Yamada, Mutsuhiro Shima, Yutaka Ohya, Teruo Ono

    Physical Review Materials   Vol. 4 ( 7 )   2020.7

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    DOI: 10.1103/PhysRevMaterials.4.074402

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  44. Tunable Magnon-Magnon Coupling Mediated by Dynamic Dipolar Interaction in Synthetic Antiferromagnets Reviewed

    Yoichi Shiota, Tomohiro Taniguchi, Mio Ishibashi, Takahiro Moriyama, Teruo Ono

    Physical Review Letters   Vol. 125 ( 1 )   2020.7

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    DOI: 10.1103/PhysRevLett.125.017203

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  45. Magnetic damping enhancement in L12-ordered Mn3Ir/Fe20Ni80 bilayers Reviewed

    Yuta Kobayashi, Tetsuya Ikebuchi, Hiroyuki Iwaki, Yoichi Shiota, Teruo Ono, Takahiro Moriyama

    Applied Physics Express   Vol. 13 ( 7 )   2020.7

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    Electron and spin transport in chiral antiferromagnets are of great interest in both fundamental and application point of views. In this letter, we explore and compare spin transport properties of a chiral antiferromagnetic L12-ordered Mn3Ir and a disordered Mn3Ir by the spin pumping experiments. Larger Gilbert damping enhancement of the Fe20Ni80 was found in L12-ordered Mn3Ir/Fe20Ni80 and L12-ordered Mn3Ir/Ti/Fe20Ni80 multilayers comparing to those with disordered ones. Our results suggest that the chiral spin structure causes larger spin dissipation than disordered spin structure.

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  46. Enhancement of spin wave group velocity in ferrimagnets with angular momentum compensation Reviewed

    Shinsaku Funada, Yoichi Shiota, Mio Ishibashi, Takahiro Moriyama, Teruo Ono

    Applied Physics Express   Vol. 13 ( 6 )   2020.6

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    In this study, we theoretically investigated properties of magnetostatic spin waves in rare-earth and transition-metal ferrimagnets with various angular momentum. The resonant frequency of high-(low-) frequency mode has the lowest (highest) value at angular momentum compensation temperature (T ). It was found that both resonance modes show a maximum group velocity at T . Furthermore, the low-frequency mode shows higher group velocity than the high-frequency mode at any temperature. Our findings are the key to advance both the physics and the technology to develop research field of magnonics based on the antiferromagnetic spin waves. A A

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  47. Imaging of caustic-like spin wave beams using optical heterodyne detection Reviewed

    Yoichi Shiota, Shinsaku Funada, Ryusuke Hisatomi, Takahiro Moriyama, Teruo Ono

    Applied Physics Letters   Vol. 116 ( 19 )   2020.5

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    We investigated caustic-like spin wave beams radiated from a narrow waveguide to a continuous film using a Permalloy. For this purpose, we developed a spatially resolved optical heterodyne detection of propagating spin waves by using the polar Kerr effect, which allows the measurement of the intensity and the phase information of the spin waves. We characterized magnetostatic surface spin wave modes in one-dimensional (1D) propagation and caustic-like spin wave beams in two-dimensional (2D) propagation as a function of excitation frequency. The fast Fourier transformations of the real space images reconstruct 1D and 2D spin wave dispersion, which agree with the theoretical calculations.

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  48. Distinct domain reversal mechanisms in epitaxial and polycrystalline antiferromagnetic NiO films from high-field spin Hall magnetoresistance Reviewed

    Takahiro Moriyama

    Applied Physics Letters   Vol. 116 ( 19 ) page: 192402 - 192402   2020.5

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    DOI: 10.1063/1.5142495

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  49. Switchable giant nonreciprocal frequency shift of propagating spin waves in synthetic antiferromagnets Reviewed

    Mio Ishibashi, Yoichi Shiota, Tian Li, Shinsaku Funada, Takahiro Moriyama, Teruo Ono

    Science Advances   Vol. 6 ( 17 ) page: eaaz6931 - eaaz6931   2020.4

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    The nonreciprocity of propagating spin waves, i.e., the difference in amplitude and/or frequency depending on the propagation direction, is essential for the realization of spin wave–based logic circuits. However, the nonreciprocal frequency shifts demonstrated so far are not large enough for applications because they originate from interfacial effects. In addition, switching of the spin wave nonreciprocity in the electrical way remains a challenging issue. Here, we show a switchable giant nonreciprocal frequency shift of propagating spin waves in interlayer exchange–coupled synthetic antiferromagnets. The observed frequency shift is attributed to large asymmetric spin wave dispersion caused by a mutual dipolar interaction between two magnetic layers. Furthermore, we find that the sign of the frequency shift depends on relative configuration of two magnetizations, based on which we demonstrate an electrical switching of the nonreciprocity. Our findings provide a route for switchable and highly nonreciprocal spin wave–based applications.

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  50. Giant Anomalous Hall Conductivity at the Pt/Cr 2 O 3 Interface Reviewed

    Takahiro Moriyama, Yu Shiratsuchi, Tatsuya Iino, Hikaru Aono, Motohiro Suzuki, Tetsuya Nakamura, Yoshinori Kotani, Ryoichi Nakatani, Kohji Nakamura, Teruo Ono

    Physical Review Applied   Vol. 13 ( 3 )   2020.3

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    DOI: 10.1103/PhysRevApplied.13.034052

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  51. Enhanced antiferromagnetic resonance linewidth in NiO/Pt and NiO/Pd Reviewed

    Takahiro Moriyama, Kensuke Hayashi, Keisuke Yamada, Mutsuhiro Shima, Yutaka Ohya, Yaroslav Tserkovnyak, Teruo Ono

    Physical Review B   Vol. 101 ( 6 )   2020.2

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    DOI: 10.1103/PhysRevB.101.060402

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  52. Field-sweep-rate and time dependence of transverse resistivity anomalies in ultrathin SrRuO3 films Reviewed

    Daisuke Kan, Takahiro Moriyama, Yuichi Shimakawa

    Physical Review B   Vol. 101 ( 1 )   2020.1

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    DOI: 10.1103/PhysRevB.101.014448

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  53. Large anomalous Hall effect in L12-ordered antiferromagnetic Mn3Ir thin films Reviewed

    Hiroyuki Iwaki, Motoi Kimata, Tetsuya Ikebuchi, Yuta Kobayashi, Kent Oda, Yoichi Shiota, Teruo Ono, Takahiro Moriyama

    Applied Physics Letters   Vol. 116 ( 2 )   2020.1

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    DOI: 10.1063/1.5128241

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  54. Elastic constants of beta tungsten thin films studied by picosecond ultrasonics and density functional theory Reviewed

    A. Nagakubo, H. T. Lee, H. Ogi, T. Moriyama, T. Ono

    Applied Physics Letters   Vol. 116 ( 2 )   2020.1

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    DOI: 10.1063/1.5131768

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  55. Fabrication of Ferrimagnetic Co/Gd/Pt Multilayers with Structural Inversion Symmetry Breaking Reviewed

    T. Nishimura, M. Haruta, D.-H. Kim, Y. Shiota, H. Iwaki, D. Kan, T. Moriyama, H. Kurata, T. Ono

    Journal of the Magnetics Society of Japan   Vol. 44 ( 1 ) page: 9 - 14   2020.1

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    We developed ferrimagnetic [Co(0.5)/Gd(1)/Pt(1)]N (unit: nm) multilayers with structural inversion symmetry breaking and investigated the dependence of magnetic properties and magnetic domain structures on the repetition number (N = 1 – 50). The magnetization compensation temperature increases as N increases, and saturates at around 210 K for N ≥ 20. All films with various repetition number possess the out-of-plane magnetic easy axis, and multi domain structure at the remanence state was observed in the film with N = 50. These results show that the magnetic properties of the ferrimagnetic Co/Gd/Pt multilayers can be tuned by the repetition number.

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  56. Temperature dependence of spin Hall magnetoresistance across the Néel temperature of CoO Reviewed

    Oda Kent, MORIYAMA Takahiro, Kimata Motoi, Kasukawa Shuhei, ONO Teruo

    Japanese Journal of Applied Physics   Vol. 59 ( 1 ) page: 010908   2019.12

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    DOI: 10.7567/1347-4065/ab6505

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  57. Spin Seebeck Imaging of Spin-Torque Switching in Antiferromagnetic Pt/NiO Heterostructures Reviewed

    Takahiro Moriyama

    Physical Review X   Vol. 9 ( 4 )   2019.10

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    DOI: 10.1103/physrevx.9.041016

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  58. Temperature dependence of magnetic resonance in ferrimagnetic GdFeCo alloys Reviewed

    Okuno Takaya, Kim Se Kwon, Moriyama Takahiro, Kim Duck-Ho, Mizuno Hayato, Ikebuchi Tetsuya, Hirata Yuushou, Yoshikawa Hiroki, Tsukamoto Arata, Kim Kab-Jin, Shiota Yoichi, Lee Kyung-Jin, Ono Teruo

    APPLIED PHYSICS EXPRESS   Vol. 12 ( 9 )   2019.9

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    We provide a macroscopic theory and experimental results for magnetic resonances of antiferromagnetically-coupled ferrimagnets. Our theory, which interpolates the dynamics of antiferromagnets and ferromagnets smoothly, can describe ferrimagnetic resonances across the angular momentum compensation point. We also present experimental results for spin-torque induced ferrimagnetic resonance at several temperatures. The spectral analysis based on our theory reveals that the Gilbert damping parameter, which has been considered to be strongly temperature dependent, is insensitive to temperature. We envision that our work will facilitate further investigation of ferrimagnetic dynamics by providing a theoretical framework suitable for a broad range of temperatures.

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  59. Spin-transfer torques for domain wall motion in antiferromagnetically coupled ferrimagnets Reviewed

    Okuno Takaya, Kim Duck-Ho, Oh Se-Hyeok, Kim Se Kwon, Hirata Yuushou, Nishimura Tomoe, Ham Woo Seung, Futakawa Yasuhiro, Yoshikawa Hiroki, Tsukamoto Arata, Tserkovnyak Yaroslav, Shiota Yoichi, Moriyama Takahiro, Kim Kab-Jin, Lee Kyung-Jin, Ono Teruo

    NATURE ELECTRONICS   Vol. 2 ( 9 ) page: 389 - 393   2019.9

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    Antiferromagnetic materials offer ultrafast spin dynamics and could be used to build devices that are orders of magnitude faster than those based on ferromagnetic materials. Spin-transfer torque is key to the electrical control of spins and has been demonstrated in ferromagnetic spintronics. However, experimental exploration of spin-transfer torque in antiferromagnets remains limited, despite a number of theoretical studies. Here, we report an experimental examination of the effects of spin-transfer torque on the motion of domain walls in antiferromagnetically coupled ferrimagnets. Using a ferrimagnetic gadolinium–iron–cobalt (GdFeCo) alloy in which Gd and FeCo moments are coupled antiferromagnetically, we find that non-adiabatic spin-transfer torque acts like a staggered magnetic field, providing efficient control of the domain walls. We also show that the non-adiabaticity parameter of the spin-transfer torque is significantly larger than the Gilbert damping parameter, in contrast to the case of non-adiabatic spin-transfer torque in ferromagnets.

    DOI: 10.1038/s41928-019-0303-5

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  60. Spin wave propagation in ferrimagnetic GdxCo1-x Reviewed

    Funada Shinsaku, Nishimura Tomoe, Shiota Yoichi, Kasukawa Shuhei, Ishibashi Mio, Moriyama Takahiro, Ono Teruo

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 58 ( 8 )   2019.8

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    Recent advances in antiferromagnetic spin dynamics using rare-earth (RE) and transition-metal (TM) ferrimagnets have attracted much interest for spintronic devices with a high speed and density. In this study, the spin wave properties in the magnetostatic backward volume mode and surface mode in RE-TM ferrimagnetic GdxCo1-x films with various composition x are investigated using spin wave spectroscopy. The obtained group velocity and attenuation length are well explained by the ferromagnet-based spin wave theory when the composition of GdxCo1-x is far from the compensation point. (C) 2019 The Japan Society of Applied Physics

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  61. Magnetic properties of ferrimagnetic Tb/CoFeB/MgO films Reviewed

    Shiota Yoichi, Moriyama Takahiro, Ono Teruo

    APPLIED PHYSICS EXPRESS   Vol. 12 ( 8 )   2019.8

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    We studied perpendicular magnetic anisotropy (PMA) and magnetization compensation temperature (T ) in Tb/CoFeB/MgO films. Interlayer antiferromagnetic coupling between Tb and CoFeB layers enables useful antiferromagnetic properties containing a CoFeB/MgO junctions, which are important for the practical applications to obtain giant tunnel magnetoresistance and voltage-control of magnetic anisotropy. While the PMA is mainly attributed to the interface at CoFeB/MgO, T can be controlled by the thickness ratio of Tb and CoFeB layers as the magnetic moments of them are antiferromagnetically coupled. Our results provide many possibilities to add exciting new functions to ferrimagnetic spintronics. M M

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  62. Bulk Dzyaloshinskii-Moriya interaction in amorphous ferrimagnetic alloys Reviewed

    Kim Duck-Ho, Haruta Mitsutaka, Ko Hye-Won, Go Gyungchoon, Park Hyeon-Jong, Nishimura Tomoe, Kim Dae-Yun, Okuno Takaya, Hirata Yuushou, Futakawa Yasuhiro, Yoshikawa Hiroki, Ham Wooseung, Kim Sanghoon, Kurata Hiroki, Tsukamoto Arata, Shiota Yoichi, Moriyama Takahiro, Choe Sug-Bong, Lee Kyung-Jin, Ono Teruo

    NATURE MATERIALS   Vol. 18 ( 7 ) page: 685 - +   2019.7

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    Symmetry breaking is a fundamental concept that prevails in many branches of physics . In magnetic materials, broken inversion symmetry induces the Dzyaloshinskii–Moriya interaction (DMI), which results in fascinating physical behaviours with the potential for application in future spintronic devices . Here, we report the observation of a bulk DMI in GdFeCo amorphous ferrimagnets. The DMI is found to increase linearly with an increasing thickness of the ferrimagnetic layer, which is a clear signature of the bulk nature of DMI. We also found that the DMI is independent of the interface between the heavy metal and ferrimagnetic layer. This bulk DMI is attributed to an asymmetric distribution of the elemental content in the GdFeCo layer, with spatial inversion symmetry broken throughout the layer. We expect that our experimental identification of a bulk DMI will open up additional possibilities to exploit this interaction in a wide range of materials. 1–5 6–14 15–17

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  63. Enhanced perpendicular magnetocrystalline anisotropy energy in an artificial magnetic material with bulk spin-momentum coupling Reviewed

    Pradipto Abdul-Muizz, Yakushiji Kay, Ham Woo Seung, Kim Sanghoon, Shiota Yoichi, Moriyama Takahiro, Kim Kyoung-Whan, Lee Hyun-Woo, Nakamura Kohji, Lee Kyung-Jin, Ono Teruo

    PHYSICAL REVIEW B   Vol. 99 ( 18 )   2019.5

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    We systematically investigate the perpendicular magnetocrystalline anisotropy (MCA) in Co-Pt/Pd-based multilayers. Our magnetic measurement data show that the asymmetric Co/Pd/Pt multilayer has a significantly larger perpendicular magnetic anisotropy (PMA) energy compared to the symmetric Co/Pt and Co/Pd multilayer samples. We further support this experiment by first-principles calculations on CoPt2, CoPd2, and CoPtPd, which are composite bulk materials that consist of three atomic layers in a unit cell, Pt/Co/Pt, Pd/Co/Pd, and Pt/Co/Pd, respectively. By estimating the contribution of bulk spin-momentum coupling to the MCA energy, we show that the CoPtPd multilayer with symmetry breaking has a significantly larger PMA energy than the other multilayers that are otherwise similar but lack symmetry breaking. This observation thus provides evidence of the PMA enhancement due to the structural inversion symmetry breaking and highlights the asymmetric CoPtPd as an artificial magnetic material with bulk spin-momentum coupling, which opens a pathway toward the design of materials with strong PMA.

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  64. Intrinsic and extrinsic antiferromagnetic damping in NiO Reviewed

    Moriyama, Takahiro, Hayashi, Kensuke, Yamada, Keisuke, Shima, Mutsuhiro, Ohya, Yutaka, Ono, Teruo

    PHYSICAL REVIEW MATERIALS   Vol. 3 ( 5 )   2019.5

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    In antiferromagnetic spintronics where manipulation of the antiferromagnetic spins is a central technological challenge, it is important to understand the dynamic properties, especially their THz spin dynamics and the magnetic damping. Here, we investigate thoroughly the antiferromagnetic spin dynamics in NiO by broadband THz spectroscopy and find the remarkable difference in the damping constants alpha = 5.0 +/- 0.4 x 10(-4) and 7.4 +/- 0.4 x 10(-4), respectively, for mono- and polycrystalline NiO, indicating the existence of strong extrinsic contributions to the damping, such as two-magnon scattering. Our results shed light on the mechanism of the antiferromagnetic dissipative dynamics and give important insights for developing antiferromagnetic and THz spintronics devices.

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  65. Low Magnetic Damping of Ferrimagnetic GdFeCo Alloys Reviewed

    Kim Duck-Ho, Okuno Takaya, Kim Se Kwon, Oh Se-Hyeok, Nishimura Tomoe, Hirata Yuushou, Futakawa Yasuhiro, Yoshikawa Hiroki, Tsukamoto Arata, Tserkovnyak Yaroslav, Shiota Yoichi, Moriyama Takahiro, Kim Kab-Jin, Lee Kyung-Jin, Ono Teruo

    PHYSICAL REVIEW LETTERS   Vol. 122 ( 12 )   2019.3

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    We investigate the Gilbert damping parameter α for rare earth (RE)-transition metal (TM) ferrimagnets over a wide temperature range. Extracted from the field-driven magnetic domain-wall mobility, α was as low as the order of 10-3 and was almost constant across the angular momentum compensation temperature TA, starkly contrasting previous predictions that α should diverge at TA due to a vanishing total angular momentum. Thus, magnetic damping of RE-TM ferrimagnets is not related to the total angular momentum but is dominated by electron scattering at the Fermi level where the TM has a dominant damping role. This low value of the Gilbert damping parameter suggests that ferrimagnets can serve as versatile platforms for low-dissipation high-speed magnetic devices.

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  66. Vanishing skyrmion Hall effect at the angular momentum compensation temperature of a ferrimagnet Reviewed

    Hirata Yuushou, Kim Duck-Ho, Kim Se Kwon, Lee Dong-Kyu, Oh Se-Hyeok, Kim Dae-Yun, Nishimura Tomoe, Okuno Takaya, Futakawa Yasuhiro, Yoshikawa Hiroki, Tsukamoto Arata, Tserkovnyak Yaroslav, Shiota Yoichi, Moriyama Takahiro, Choe Sug-Bong, Lee Kyung-Jin, Ono Teruo

    NATURE NANOTECHNOLOGY   Vol. 14 ( 3 ) page: 232 - +   2019.3

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    In the presence of a magnetic field, the flow of charged particles in a conductor is deflected from the direction of the applied force, which gives rise to the ordinary Hall effect. Analogously, moving skyrmions with non-zero topological charges and finite fictitious magnetic fields exhibit the skyrmion Hall effect, which is detrimental for applications such as skyrmion racetrack memory. It was predicted that the skyrmion Hall effect vanishes for antiferromagnetic skyrmions because their fictitious magnetic field, proportional to net spin density, is zero. Here we investigate the current-driven transverse elongation of pinned ferrimagnetic bubbles. We estimate the skyrmion Hall effect from the angle between the current and the bubble elongation directions. The angle and, hence, the skyrmion Hall effect vanishes at the angular momentum compensation temperature where the net spin density vanishes. Furthermore, our study establishes a direct connection between the fictitious magnetic field and the spin density.

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  67. Fabrication of Noncentrosymmetric Nb/V/Ta Superlattice and its Superconductivity Reviewed

    F. Ando, D. Kan, Y. Shiota, T. Moriyama, Y. Shimakawa, T. Ono

    Journal of the Magnetics Society of Japan   Vol. 44 ( 1 ) page: 9 - 14   2019.2

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  68. Resistive detection of the Néel temperature of Cr2O3 thin films Reviewed

    Tatsuya Iino, Takahiro Moriyama, Hiroyuki Iwaki, Hikaru Aono, Yu Shiratsuchi, Teruo Ono

    Applied Physics Letters   Vol. 114 ( 2 ) page: 022402 - 022402   2019.1

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    Although bulk magnetic properties of various antiferromagnets have been vigorously studied since long ago, their properties in the form of thin films, which are more relevant to antiferromagnetic spintronic devices, have not been investigated as much. In this work, we characterized the Néel temperature of Cr O thin films by investigating the temperature dependence of the spin Hall magnetoresistance in Cr O /Pt bilayers. A precise determination of the Néel temperature was made possible by carefully designing the direction of the magnetic anisotropy in Cr O . The results provide a reliable way to determine the Néel temperature of antiferromagnetic thin films. 2 3 2 3 2 3

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  69. Choking Nonlocal Magnetic Damping in Exchange-Biased Ferromagnets Reviewed

    Moriyama Takahiro, Oda Kent, Ono Teruo

    PHYSICAL REVIEW APPLIED   Vol. 11 ( 1 )   2019.1

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    We investigate the temperature dependence of the magnetic damping in exchange-biased Pt/Fe50Mn50/Fe20Ni80/SiOx multilayers. In samples having a strong exchange bias, we observed a drastic decrease of the magnetic damping of Fe-Ni with increasing temperature up to the blocking temperature. The results essentially indicate that the nonlocal enhancement of the magnetic damping can be choked by the adjacent antiferromagnet and its temperature-dependent exchange bias. We also point out that such a strong temperature-dependent damping may be very beneficial for spintronic applications.

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  70. Possible contribution of high-energy magnons to unidirectional magnetoresistance in metallic bilayers Reviewed

    Kab Jin Kim, Tian Li, Sanghoon Kim, Takahiro Moriyama, Tomohiro Koyama, Daichi Chiba, Kyung Jin Lee, Hyun Woo Lee, Teruo Ono

    Applied Physics Express   Vol. 12 ( 6 )   2019

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    © 2019 The Japan Society of Applied Physics. We investigate temperature, temporal and magnetic-field dependence of unidirectional magnetoresistance (UMR) in metallic bilayers. The UMR is found to decrease rapidly with reducing temperature and converges to a finite value at low-temperature limit. The temporal dependence shows that the UMR emerges in a nanosecond time scale, which depends on the current amplitude. The magnetic-field dependence shows that the UMR is almost constant up to 5 T. These experimental results imply that the high-energy magnons, which are not considered in existing theory, can be involved in the observed UMR. Our results therefore suggest that a more extended theory is required for the complete understanding of UMR.

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  71. Fabrication of noncentrosymmetric NB/V/Ta superlattice and its superconductivity

    Ando F., Kan D., Shiota Y., Moriyama T., Shimakawa Y., Ono T.

    Journal of the Magnetics Society of Japan   Vol. 43 ( 2 ) page: 17 - 20   2019

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    Nb, V, and Ta are all well-known superconducting elements in a simple substance. We report the superconductivity of Nb/V/Ta superlattices sputtered onto MgO(100) substrates, in which global inversion symmetry was broken along the stacking direction. It was found that the superlattices had long-range crystalline coherence with the well-defined periodicity of the constituent layers, and they exhibited superconducting transition despite the thicknesses of the layers.

    DOI: 10.3379/msjmag.1903L001

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  72. Magnetic domain writing defined by electrical gating in Pt/Co film Reviewed

    Fuyuki Ando, Mio Ishibashi, Tomohiro Koyama, Yoichi Shiota, Takahiro Moriyama, Daichi Chiba, Teruo Ono

    APPLIED PHYSICS LETTERS   Vol. 113 ( 25 )   2018.12

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    There is a need to control magnetic properties at a desired location in a magnetic film towards a realization of fundamental devices, such as domain wall logic or magnonic applications. Here, we demonstrate the formation of a magnetic domain structure at a desired location in a Pt/Co film, using electrical gating with a meshed gate electrode and sweeping the applied magnetic field. As the magnetic properties can be changed by modulating the electron density at the surface of the Co layer, this method in principle provides higher speed and power-efficient operation in inducing a nanoscale domain structure or in configuring a volatile magnonic crystal. Published by AIP Publishing.

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  73. Alternative to the topological interpretation of the transverse resistivity anomalies in SrRuO3 Reviewed

    Daisuke Kan, Takahiro Moriyama, Kento Kobayashi, Yuichi Shimakawa

    Physical Review B   Vol. 98 ( 18 )   2018.11

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    DOI: 10.1103/physrevb.98.180408

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    Other Link: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.98.180408/fulltext

  74. Magnetoresistance in Bilayers of Heavy Metal and Non-collinear Antiferromagnet Reviewed

    K. Oda, T. Moriyama, T. Ono

    Journal of the Magnetics Society of Japan   Vol. 43 ( 1 ) page: 1 - 5   2018.11

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    We report on magnetoresistance measurements in a heavy metal/ Mn3Ir multilayers. After a post annealing process, we observed the magnetoresistance associated with the ordered crystalline structure of the Mn3Ir. The resistance change as a function of the strength as well as the direction of the applied field suggests that the magnetoresistance is partially related to a modification of the Néel order by the magnetic field. Our further detailed investigation revealed that there is an additional component of the resistance change, perhaps due to the non-collinear magnetic structure associated with the L12-ordered Mn3Ir, which cannot be accounted for by any conventional magnetoresistance effects.

    DOI: 10.3379/msjmag.1901R001

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  75. Spin-Orbit-Torque Memory Operation of Synthetic Antiferromagnets Reviewed

    Moriyama, Takahiro, Zhou, Weinan, Seki, Takeshi, Takanashi, Koki, Ono, Teruo

    Physical Review Letters   Vol. 121 ( 16 ) page: 167202 - 167202   2018.10

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    DOI: 10.1103/PhysRevLett.121.167202

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    Other Link: http://orcid.org/0000-0001-7071-0823

  76. Spin current transmission in polycrystalline NiO films Reviewed

    Tetsuya Ikebuchi, Takahiro Moriyama, Hayato Mizuno, Kent Oda, Teruo Ono

    Applied Physics Express   Vol. 11 ( 7 )   2018.7

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    Spin current transmission in antiferromagnetic materials is one of the important and intriguing problems in the recently emerged field of antiferromagnetic spintronics. We investigate the spin current transmission in polycrystalline NiO by referencing the effective Gilbert damping constant in NiO/FeNi bilayers. The results are discussed with reference to the spin pumping theory assuming that the NiO layer is spin diffusive. We extracted the spin diffusion length of &gt
    22 nm for the NiO and the mixing conductance of &gt
    6 nm%2 at the NiO/FeNi interface. The obtained spin diffusion length and the mixing conductance are within reasonable ranges compared with previous reports.

    DOI: 10.7567/APEX.11.073003

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  77. Microscopic origin of electric-field-induced modulation of Curie temperature in cobalt Reviewed

    Fuyuki Ando, Kihiro T. Yamada, Tomohiro Koyama, Mio Ishibashi, Yoichi Shiota, Takahiro Moriyama, Daichi Chiba, Teruo Ono

    APPLIED PHYSICS EXPRESS   Vol. 11 ( 7 )   2018.7

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    The Curie temperature Tc is one of the most fundamental physical properties of ferromagnetic materials and can be described by the Weiss molecular field theory with the exchange interaction of neighboring atoms. Here, we demonstrate the electrical control of exchange coupling in cobalt films through direct magnetization measurements. We find that the reduction in magnetization with temperature, which is caused by thermal spin wave excitation and scales with Bloch's law, dearly depends on the applied electric field. Furthermore, we confirm that the correlation between the electric-field-induced modulation of Tc and that of exchange coupling follows the Weiss molecular field theory. (C) 2018 The Japan Society of Applied Physics

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  78. Effect of depinning field on determination of angular-momentum-compensation temperature of ferrimagnets Reviewed

    Yuushou Hirata, Duck-Ho Kim, Takaya Okuno, Tomoe Nishimura, Yasuhiro Futakawa, Hiroki Yoshikawa, Wooseung Ham, Sanghoon Kim, Arata Tsukamoto, Yoichi Shiota, Takahiro Moriyama, Kab-Jin Kim, Teruo Ono

    Applied Physics Express   Vol. 11 ( 6 ) page: 063001   2018.6

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    The domain-wall (DW) motion of ferrimagnets is investigated with respect to the angular-momentum-compensation temperature TA for a wide range of magnetic fields μ0Hz, ranging from the depinning to flow regimes. While the DW velocity v exhibits a maximum at TA in the flow regime regardless of μ0Hz, the temperature at which v is maximized depends on μ0Hz because of the temperature dependence of the depinning field μ0Hdep, causing difficulty in determining TA. To solve this problem, we propose a reduced coordinate μ0Hz % μ0Hdep, which reveals that v is maximized at TA even in the depinning regime. Our work suggests that μ0Hdep should be identified prior to determining TA.

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  79. Electric field effect on exchange interaction in ultrathin Co films with ionic liquids Reviewed

    Mio Ishibashi, Kihiro T. Yamada, Yoichi Shiota, Fuyuki Ando, Tomohiro Koyama, Haruka Kakizakai, Hayato Mizuno, Kazumoto Miwa, Shimpei Ono, Takahiro Moriyama, Daichi Chiba, Teruo Ono

    APPLIED PHYSICS EXPRESS   Vol. 11 ( 6 )   2018.6

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    Electric-field modulations of magnetic properties have been extensively studied not only for practical applications but also for fundamental interest. In this study, we investigated the electric field effect on the exchange interaction in ultrathin Co films with ionic liquids. The exchange coupling J was characterized from the direct magnetization measurement as a function of temperature using Pt/ultrathin Co/MgO structures. The trend of the electric field effect on J is in good agreement with that of the theoretical prediction, and a large change in J by applying a gate voltage was observed by forming an electric double layer using ionic liquids. (C) 2018 The Japan Society of Applied Physics

    DOI: 10.7567/APEX.11.063002

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  80. Spin-wave wavelength down-conversion at thickness steps Reviewed

    Johannes Stigloher, Takuya Taniguchi, Marco Madami, Martin Decker, Helmut S. Körner, Takahiro Moriyama, Gianluca Gubbiotti, Teruo Ono, Christian H. Back

    Applied Physics Express   Vol. 11 ( 5 )   2018.5

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    We report a systematic experimental study on the refraction and reflection of magnetostatic spin-waves at a thickness step between two Permalloy films of different thickness. The transmitted spin-waves for the transition from a thick film to a thin film have a higher wave vector compared to the incoming waves. Consequently, such systems may find use as passive wavelength transformers in magnonic networks. We investigate the spin-wave transmission behavior by studying the influence of the external magnetic field, incident angle, and thickness ratio of the films using time-resolved scanning Kerr microscopy and micro-focused Brillouin light scattering.

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  81. Homodyne detection of ferromagnetic resonance by a non-uniform radio-frequency excitation current Reviewed

    Tetsuya Ikebuchi, Takahiro Moriyama, Yoichi Shiota, Teruo Ono

    Applied Physics Express   Vol. 11 ( 5 )   2018.5

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    Ferromagnetic resonance (FMR) is one of the most popular techniques to characterize dynamic properties of ferromagnetic materials. Among various FMR measurement techniques, the homodyne FMR detection has been frequently used to characterize thin-film ferromagnetic multilayers owing to its high sensitivity. However, a drawback of this technique was considered to be the requirement for a structural inversion asymmetry, which makes it unsuitable to characterize a single layer of ferromagnet. In this study, we demonstrate a homodyne FMR detection of the Kittel’s mode FMR dynamics of a single layer of FeNi by creating a non-uniform radio-frequency excitation current.

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  82. Determination of perpendicular magnetic anisotropy based on the magnetic droplet nucleation Reviewed

    Tomoe Nishimura, Duck-Ho Kim, Takaya Okuno, Yuushou Hirata, Yasuhiro Futakawa, Hiroki Yoshikawa, Sanghoon Kim, Arata Tsukamoto, Yoichi Shiota, Takahiro Moriyama, Teruo Ono

    Japanese Journal of Applied Physics   Vol. 57 ( 5 )   2018.5

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    We propose an alternative method of determining the magnetic anisotropy field μ0HK in ferro-/ferrimagnets. On the basis of the droplet nucleation model, there exists linearity between domain-wall (DW) energy density and in-plane magnetic field. We find that the slope is simply represented by μ0HK and Dzyaloshinskii–Moriya interaction (DMI). By measuring the in-plane magnetic field dependence of the coercivity field, closely corresponding to the DW energy density, a robust value for μ0HK can be quantified. This robust value can be used to determine μ0HK over a wide range of values, overcoming the limitations caused by the small strength of the external magnetic field typically used in experiments.

    DOI: 10.7567/JJAP.57.050308

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  83. Correlation of the Dzyaloshinskii-Moriya interaction with Heisenberg exchange and orbital asphericity. Reviewed International journal

    Sanghoon Kim, Kohei Ueda, Gyungchoon Go, Peong-Hwa Jang, Kyung-Jin Lee, Abderrezak Belabbes, Aurelien Manchon, Motohiro Suzuki, Yoshinori Kotani, Tetsuya Nakamura, Kohji Nakamura, Tomohiro Koyama, Daichi Chiba, Kihiro T Yamada, Duck-Ho Kim, Takahiro Moriyama, Kab-Jin Kim, Teruo Ono

    Nature communications   Vol. 9 ( 1 ) page: 1648 - 1648   2018.4

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    Chiral spin textures of a ferromagnetic layer in contact to a heavy non-magnetic metal, such as Néel-type domain walls and skyrmions, have been studied intensively because of their potential for future nanomagnetic devices. The Dyzaloshinskii-Moriya interaction (DMI) is an essential phenomenon for the formation of such chiral spin textures. In spite of recent theoretical progress aiming at understanding the microscopic origin of the DMI, an experimental investigation unravelling the physics at stake is still required. Here we experimentally demonstrate the close correlation of the DMI with the anisotropy of the orbital magnetic moment and with the magnetic dipole moment of the ferromagnetic metal in addition to Heisenberg exchange. The density functional theory and the tight-binding model calculations reveal that inversion symmetry breaking with spin-orbit coupling gives rise to the orbital-related correlation. Our study provides the experimental connection between the orbital physics and the spin-orbit-related phenomena, such as DMI.

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  84. Correlation between magnetic properties and depinning field in field-driven domain wall dynamics in GdFeCo ferrimagnets Reviewed

    Tomoe Nishimura, Duck-Ho Kim, Yuushou Hirata, Takaya Okuno, Yasuhiro Futakawa, Hiroki Yoshikawa, Arata Tsukamoto, Yoichi Shiota, Takahiro Moriyama, Teruo Ono

    Applied Physics Letters   Vol. 112 ( 17 )   2018.4

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    The influence of temperature on the magnetic-field-driven domain wall motion is investigated in GdFeCo ferrimagnets with perpendicular magnetic anisotropy (PMA). We find that the depinning field strongly depends on temperature. Moreover, it is also found that the saturation magnetization exhibits a similar dependence on temperature to that of the depinning field. From the creep-scaling criticality, a simple relation between the depinning field and the properties of PMA is clearly identified theoretically as well as experimentally. Our findings open a way for a better understanding of how the magnetic properties influence the depinning field in the magnetic system and would be valuably extended to depinning studies in other systems.

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  85. Microscopic Investigation into the Electric Field Effect on Proximity-Induced Magnetism in Pt Reviewed

    K. T. Yamada, M. Suzuki, A. M. Pradipto, T. Koyama, S. Kim, K. J. Kim, S. Ono, T. Taniguchi, H. Mizuno, F. Ando, K. Oda, H. Kakizakai, T. Moriyama, K. Nakamura, D. Chiba, T. Ono

    Physical Review Letters   Vol. 120 ( 15 )   2018.4

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    Electric field effects on magnetism in metals have attracted widespread attention, but the microscopic mechanism is still controversial. We experimentally show the relevancy between the electric field effect on magnetism and on the electronic structure in Pt in a ferromagnetic state using element-specific measurements: x-ray magnetic circular dichroism (XMCD) and x-ray absorption spectroscopy (XAS). Electric fields are applied to the surface of ultrathin metallic Pt, in which a magnetic moment is induced by the ferromagnetic proximity effect resulting from a Co underlayer. XMCD and XAS measurements performed under the application of electric fields reveal that both the spin and orbital magnetic moments of Pt atoms are electrically modulated, which can be explained not only by the electric-field-induced shift of the Fermi level but also by the change in the orbital hybridizations.

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  86. Antiferromagnetic spintronics Reviewed

    V. Baltz, A. Manchon, M. Tsoi, T. Moriyama, T. Ono, Y. Tserkovnyak

    Reviews of Modern Physics   Vol. 90 ( 1 )   2018.2

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    Antiferromagnetic materials could represent the future of spintronic applications thanks to the numerous interesting features they combine: they are robust against perturbation due to magnetic fields, produce no stray fields, display ultrafast dynamics, and are capable of generating large magnetotransport effects. Intense research efforts over the past decade have been invested in unraveling spin transport properties in antiferromagnetic materials. Whether spin transport can be used to drive the antiferromagnetic order and how subsequent variations can be detected are some of the thrilling challenges currently being addressed. Antiferromagnetic spintronics started out with studies on spin transfer and has undergone a definite revival in the last few years with the publication of pioneering articles on the use of spin-orbit interactions in antiferromagnets. This paradigm shift offers possibilities for radically new concepts for spin manipulation in electronics. Central to these endeavors are the need for predictive models, relevant disruptive materials, and new experimental designs. This paper reviews the most prominent spintronic effects described based on theoretical and experimental analysis of antiferromagnetic materials. It also details some of the remaining bottlenecks and suggests possible avenues for future research. This review covers both spin-transfer-related effects, such as spin-transfer torque, spin penetration length, domain-wall motion, and "magnetization" dynamics, and spin-orbit related phenomena, such as (tunnel) anisotropic magnetoresistance, spin Hall, and inverse spin galvanic effects. Effects related to spin caloritronics, such as the spin Seebeck effect, are linked to the transport of magnons in antiferromagnets. The propagation of spin waves and spin superfluids in antiferromagnets is also covered.

    DOI: 10.1103/RevModPhys.90.015005

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  87. Spin torque in FeRh alloy measured by spin-torque ferromagnetic resonance Reviewed

    Kensho Tanaka, Takahiro Moriyama, Takamasa Usami, Tomoyasu Taniyama, Teruo Ono

    Applied Physics Express   Vol. 11 ( 1 )   2018.1

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    Spin injection into 3d transition metals and their alloys has been investigated intensively in recent years. In this study, we focus on the FeRh alloy, which is often used in the context of antiferromagnetic spintronics. We explore the interaction between the spin current and magnetic moments in FeRh by means of spin-torque ferromagnetic resonance. We obtain a spin Hall efficiency of ξSH = 24 ± 3%, which indicates that the spin current from Pt interacts with the magnetic moments in FeRh.

    DOI: 10.7567/APEX.11.013008

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  88. Spin torque control of antiferromagnetic moments in NiO Reviewed

    Moriyama, T., Oda, K., Ohkochi, T., Kimata, M., Ono, T.

    Scientific Reports   Vol. 8 ( 1 )   2018

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    DOI: 10.1038/s41598-018-32508-w

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  89. Observation of a Goos-Hänchen-like Phase Shift for Magnetostatic Spin Waves Reviewed

    Stigloher, J., Taniguchi, T., K{\"o}rner, H.S., Decker, M., Moriyama, T., Ono, T., Back, C.H.

    Physical Review Letters   Vol. 121 ( 13 )   2018

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    DOI: 10.1103/PhysRevLett.121.137201

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  90. Evaluation of electric field effect on interface magnetic properties by propagating spin wave in Pt/Co/MgO structures Reviewed

    Kasukawa, S., Shiota, Y., Moriyama, T., Ono, T.

    Japanese Journal of Applied Physics   Vol. 57 ( 8 )   2018

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    DOI: 10.7567/JJAP.57.080309

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  91. Magnetic Moment Orientation-Dependent Spin Dissipation in Antiferromagnets Reviewed

    Takahiro Moriyama, Michinari Kamiya, Kent Oda, Kensho Tanaka, Kab-Jin Kim, Teruo Ono

    PHYSICAL REVIEW LETTERS   Vol. 119 ( 26 )   2017.12

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    Spin interaction in antiferromagnetic materials is of central interest in the recently emerging antiferromagnetic spintronics. In this Letter, we explore the spin current interaction in antiferromagnetic FeMn by the spin pumping effect. Exchange biased FeNi/FeMn films, in which the Neel vector can be presumably controlled via the exchange spring effect, are employed to investigate the damping enhancement depending on the relative orientation between the Neel vector and the polarization of the pumped spin current. The correlation between the enhanced damping and the strength of the exchange bias suggests that the twisting of the Neel vector induces an additional spin dissipation, which verifies that the Slonczewski-type spin torque is effective even in antiferromagnetic materials.

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  92. Fast domain wall motion in the vicinity of the angular momentum compensation temperature of ferrimagnets Reviewed

    Kab-Jin Kim, Se Kwon Kim, Yuushou Hirata, Se-Hyeok Oh, Takayuki Tono, Duck-Ho Kim, Takaya Okuno, Woo Seung Ham, Sanghoon Kim, Gyoungchoon Go, Yaroslav Tserkovnyak, Arata Tsukamoto, Takahiro Moriyama, Kyung-Jin Lee, Teruo Ono

    NATURE MATERIALS   Vol. 16 ( 12 ) page: 1187 - +   2017.12

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    Antiferromagnetic spintronics is an emerging research field which aims to utilize antiferromagnets as core elements in spintronic devices(1,2). A central motivation towards this direction is that antiferromagnetic spin dynamics is expected to be much faster than its ferromagnetic counterpart(3). Recent theories indeed predicted faster dynamics of antiferromagnetic domain walls (DWs) than ferromagnetic DWs(4-6). However, experimental investigations of antiferromagnetic spin dynamics have remained unexplored, mainly because of the magnetic field immunity of antiferromagnets(7). Here we show that fast field-driven antiferromagnetic spin dynamics is realized in ferrimagnets at the angular momentum compensation point TA. Using rare earth-3d-transition metal ferrimagnetic compounds where net magnetic moment is nonzero at TA, the field-driven DW mobility is remarkably enhanced up to 20 km s(-1) T-1. The collective coordinate approach generalized for ferrimagnets(8) and atomistic spin model simulations(6,9) show that this remarkable enhancement is a consequence of antiferromagnetic spin dynamics at TA. Our finding allows us to investigate the physics of antiferromagnetic spin dynamics and highlights the importance of tuning of the angular momentum compensation point of ferrimagnets, which could be a key towards ferrimagnetic spintronics.

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  93. Electric-field-induced modulation of the anomalous Hall effect in a heterostructured itinerant ferromagnet SrRuO3 Reviewed

    Hayato Mizuno, Kihiro T. Yamada, Daisuke Kan, Takahiro Moriyama, Yuichi Shimakawa, Teruo Ono

    PHYSICAL REVIEW B   Vol. 96 ( 21 )   2017.12

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    We fabricated electric-field-effect transistor structures with a channel layer of an itinerant ferromagnet SrRuO3 (SRO) heterostructured with a cap layer of BaTiO3 and investigated the electric field effects on the anomalous Hall effect (AHE) in SRO. We show that by applying positive and negative gate voltages (V-G), the anomalous Hall conductivity in the heterostructured SRO increases and decreases, respectively, regardless of its sign, while no change in the magnetic easy axis direction is observed. The results indicate that the observed V-G-induced modulations of the AHE do not simply originate from changes in the magnetization and magnetic anisotropy and indicate that V-G-induced changes in an integral of the Berry curvature over the filled electronic states play a key role in the observed electric field effects on the AHE in SRO. We also found that V-G-induced modulations on the AHE are negligibly small for transistor structures with a SRO channel having no BTO cap layer. This implies that the cap-layer-induced modifications in the Ru-O-Ru bond angles in the channel affect the Berry phase, enhancing the electric field effects on the AHE in SRO.

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  94. Origin of threshold current density for asymmetric magnetoresistance in Pt/Py bilayers Reviewed

    Tian Li, Sanghoon Kim, Seung-Jae Lee, Seo-Won Lee, Tomohiro Koyama, Daichi Chiba, Takahiro Moriyama, Kyung-Jin Lee, Kab-Jin Kim, Teruo Ono

    APPLIED PHYSICS EXPRESS   Vol. 10 ( 7 )   2017.7

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    The asymmetric magnetoresistance (MR) in Py/Pt bilayers is investigated. It increases linearly with respect to the current density up to a threshold and increases more rapidly above this threshold. To reveal the origin of the threshold behavior, we investigate the magnetic field dependence of the asymmetric MR. It is found that the magnetic field strongly suppresses the asymmetric MR only above the threshold current density. Micromagnetic simulation reveals that the reduction of magnetization due to the spin-torque oscillation can be the origin of the threshold behavior of the asymmetric MR. (C) 2017 The Japan Society of Applied Physics

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  95. Contributions of Co and Fe orbitals to perpendicular magnetic anisotropy of MgO/CoFeB bilayers with Ta, W, IrMn, and Ti underlayers Reviewed

    Sanghoon Kim, Seung-heon Chris Baek, Mio Ishibashi, Kihiro Yamada, Takuya Taniguchi, Takaya Okuno, Yoshinori Kotani, Tetsuya Nakamura, Kab-Jin Kim, Takahiro Moriyama, Byong-Guk Park, Teruo Ono

    APPLIED PHYSICS EXPRESS   Vol. 10 ( 7 )   2017.7

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    We study the perpendicular magnetic anisotropy (PMA) of the CoFeB/MgO bilayers in contact with W, Ta, IrMn, and Ti, which have been suggested for use as the spin-orbit-torque-related underlayers. The saturation magnetization of CoFeB depends on the underlayer material used owing to the formation of a dead layer that affects the PMA strength of each film. The X-ray magnetic circular dichroism measurement reveals that interfacial intermixing suppresses only the perpendicular orbital moment of Fe, whereas it simultaneously suppresses both the perpendicular and in-plane orbital moments of Co. (C) 2017 The Japan Society of Applied Physics

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  96. Temperature dependence of spin-orbit effective fields in Pt/GdFeCo bilayers Reviewed

    Woo Seung Ham, Sanghoon Kim, Duck-Ho Kim, Kab-Jin Kim, Takaya Okuno, Hiroki Yoshikawa, Arata Tsukamoto, Takahiro Moriyama, Teruo Ono

    APPLIED PHYSICS LETTERS   Vol. 110 ( 24 )   2017.6

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    Harmonic Hall measurements were performed in Pt/GdFeCo bilayers to quantify the effective field resulting from the spin-orbit torque at various temperatures, both above and below the magnetization compensation temperature (T-M). We found that the damping-like torque rapidly increased near the T-M of the GdFeCo, which was attributed to a reduction in the net magnetic moment. Moreover, most importantly, the resulting spin Hall efficiency turned out to be constant across the temperature range. Published by AIP Publishing.

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  97. Magnetic droplet nucleation with a homochiral Neel domain wall Reviewed

    Sanghoon Kim, Peong-Hwa Jang, Duck-Ho Kim, Mio Ishibashi, Takuya Taniguchi, Takahiro Moriyama, Kab-Jin Kim, Kyung-Jin Lee, Teruo Ono

    PHYSICAL REVIEW B   Vol. 95 ( 22 )   2017.6

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    We investigate the effect of the Dzyaloshinskii-Moriya interaction (DMI) on magnetic domain nucleation in a ferromagnetic thin film with perpendicular magnetic anisotropy. We propose an extended droplet model to determine the nucleation field as a function of the in-plane field. The model can explain the experimentally observed nucleation in a Co/Ni microstrip with an interfacial DMI. The results are also reproduced by micromagnetic simulation based on the string model. The electrical measurement method proposed here can be widely used to quantitatively determine the DMI energy density.

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  98. Influence of sloped electric field on magnetic-field-induced domain wall creep in a perpendicularly magnetized Co wire Reviewed

    Haruka Kakizakai, Kihiro Yamada, Fuyuki Ando, Masashi Kawaguchi, Tomohiro Koyama, Sanghoon Kim, Takahiro Moriyama, Daichi Chiba, Teruo Ono

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 56 ( 5 )   2017.5

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    A creep motion of the magnetic domain wall (DW) in a perpendicularly magnetized Co wire, where the DW energy is artificially varied by applying a sloped electric field, is studied. Under the sloped electric field and a constant external magnetic field, the DW velocity gradually changes according to the position of the wire owing to the spatially varying DW energy. Although the sloped DW energy can be a source to drive a DW, no clear electric-field-induced DW motion is observed, most likely because the effective magnetic field induced by the sloped electric field is very small in the present system. (C) 2017 The Japan Society of Applied Physics

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  99. Energy-efficient writing scheme for magnetic domain-wall motion memory Reviewed

    Kab-Jin Kim, Yoko Yoshimura, Woo Seung Ham, Rick Ernst, Yuushou Hirata, Tian Li, Sanghoon Kim, Takahiro Moriyama, Yoshinobu Nakatani, Teruo Ono

    APPLIED PHYSICS EXPRESS   Vol. 10 ( 4 )   2017.4

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    We present an energy-efficient magnetic domain-writing scheme for domain wall (DW) motion-based memory devices. A cross-shaped nanowire is employed to inject a domain into the nanowire through current-induced DW propagation. The energy required for injecting the magnetic domain is more than one order of magnitude lower than that for the conventional field-based writing scheme. The proposed scheme is beneficial for device miniaturization because the threshold current for DW propagation scales with the device size, which cannot be achieved in the conventional field-based technique. (C) 2017 The Japan Society of Applied Physics

    DOI: 10.7567/APEX.10.043002

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  100. Electrical control of superparamagnetism Reviewed

    Kihiro T. Yamada, Tomohiro Koyama, Haruka Kakizakai, Kazumoto Miwa, Fuyuki Ando, Mio Ishibashi, Kab-Jin Kim, Takahiro Moriyama, Shimpei Ono, Daichi Chiba, Teruo Ono

    APPLIED PHYSICS EXPRESS   Vol. 10 ( 1 )   2017.1

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    The electric field control of superparamagnetism is realized using a Cu/Ni system, in which the deposited Ni shows superparamagnetic behavior above the blocking temperature. An electric double-layer capacitor (EDLC) with the Cu/Ni electrode and a nonmagnetic counter electrode is fabricated to examine the electric field effect on magnetism in the magnetic electrode. By changing the voltage applied to the EDLC, the blocking temperature of the system is clearly modulated. (C) 2017 The Japan Society of Applied Physics

    DOI: 10.7567/APEX.10.013004

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  101. The protective effect of human atrial natriuretic peptide on renal damage during cardiac surgery

    Takahiro Moriyama

    Journal of Anesthesia   Vol. 31 ( 2 ) page: 163 - 169   2017

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    DOI: 10.1007/S00540-016-2284-0

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  102. Room-temperature fracture toughness of MoSiBTiC alloys

    Takahiro Moriyama

    Intermetallics   Vol. 84   page: 92 - 102   2017

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    DOI: 10.1016/J.INTERMET.2017.01.004

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  103. Fast domain wall motion induced by antiferromagnetic spin dynamics at the angular momentum compensation temperature of ferrimagnets

    Takahiro Moriyama

    ArXiv     2017

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  104. Spin-orbit effective fields in Pt/GdFeCo bilayers

    Takahiro Moriyama

    ArXiv     2017

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  105. Temperature dependence of spin Hall magnetoresistance in W/CoFeB bilayer Reviewed

    Takaya Okuno, Takuya Taniguchi, Sanghoon Kim, Seung-heon Chris Baek, Byong-Guk Park, Takahiro Moriyama, Kab-Jin Kim, Teruo Ono

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 55 ( 8 )   2016.8

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    We investigate the temperature dependence of the spin Hall magnetoresistance (SMR) in a W/CoFeB bilayer. The SMR is found to increase with decreasing temperature. An analysis based on the SMR theory suggests that the spin Hall angle of W and/or the spin polarization of CoFeB can be the origin of the temperature dependence of the SMR. We also find that the spin diffusion length and the resistivity of W do not significantly vary with temperature, which indicates the necessity of further study on the electron transport mechanism in W films to reveal the origin of the spin Hall effect in W. (C) 2016 The Japan Society of Applied Physics

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  106. Temperature dependence of magnetoresistance in GdFeCo/Pt heterostructure Reviewed

    Takaya Okuno, Kab-Jin Kim, Takayuki Tono, Sanghoon Kim, Takahiro Moriyama, Hiroki Yoshikawa, Arata Tsukamoto, Teruo Ono

    APPLIED PHYSICS EXPRESS   Vol. 9 ( 7 )   2016.7

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    The temperature dependence of magnetoresistance is investigated in ferrimagnetic GdFeCo/Pt heterostructures. An anomalous Hall effect (AHE) shows a monotonic behavior in temperature even across the magnetization compensation temperature TM, implying that the FeCo moment is responsible for the magnetotransport properties. An anisotropic magnetoresistance (AMR) exhibits a steep increase at low temperatures, which we ascribe to the contribution of a weak antilocalization in an amorphous GdFeCo layer. A spin Hall magnetoresistance (SMR) is found to exist in ferrimagnet/Pt systems and shows a moderate temperature dependence, in contrast to the SMR in YIG/Pt where a significant temperature dependence was observed. These results provide a basic understanding of the magnetotransport in amorphous ferrimagnets/heavy metal heterostructures. (C) 2016 The Japan Society of Applied Physics

    DOI: 10.7567/APEX.9.073001

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  107. Snell's Law for Spin Waves Reviewed

    J. Stigloher, M. Decker, H. S. Koerner, K. Tanabe, T. Moriyama, T. Taniguchi, H. Hata, M. Madami, G. Gubbiotti, K. Kobayashi, T. Ono, C. H. Back

    PHYSICAL REVIEW LETTERS   Vol. 117 ( 3 ) page: 037204   2016.7

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    We report the experimental observation of Snell's law for magnetostatic spin waves in thin ferromagnetic Permalloy films by imaging incident, refracted, and reflected waves. We use a thickness step as the interface between two media with different dispersion relations. Since the dispersion relation for magnetostatic waves in thin ferromagnetic films is anisotropic, deviations from the isotropic Snell's law known in optics are observed for incidence angles larger than 25 degrees with respect to the interface normal between the two magnetic media. Furthermore, we can show that the thickness step modifies the wavelength and the amplitude of the incident waves. Our findings open up a new way of spin wave steering for magnonic applications.

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  108. Modulation of the magnetic domain size induced by an electric field Reviewed

    F. Ando, H. Kakizakai, T. Koyama, K. Yamada, M. Kawaguchi, S. Kim, K. -J. Kim, T. Moriyama, D. Chiba, T. Ono

    APPLIED PHYSICS LETTERS   Vol. 109 ( 2 )   2016.7

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    The electric field (EF) effect on the magnetic domain structure of a Pt/Co system was studied, where an EF was applied to the top surface of the Co layer. The width of the maze domain was significantly modified by the application of the EF at a temperature slightly below the Curie temperature. After a detailed analysis, a change in the microscopic exchange stiffness induced by the EF application was suggested to dominate the modulation of the domain width observed in the experiment. The accumulation of electrons at the surface of the Co layer resulted in an increase in the microscopic exchange stiffness and the Curie temperature. The result was consistent with the recent theoretical prediction. Published by AIP Publishing.

    DOI: 10.1063/1.4955265

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  109. Exchange bias controlled by electric current: Interplay of Joule heating and the induced field Reviewed

    Kent Oda, Takahiro Moriyama, Masashi Kawaguchi, Michinari Kamiya, Kensho Tanaka, Kab-Jin Kim, Teruo Ono

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 55 ( 7 )   2016.7

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    Exchange bias is a unidirectional magnetic anisotropy developed in a bilayer of ferromagnetic and antiferromagnetic layers. Its technical importance as a "fix layer" is seen in various spintronic devices. The exchange bias can also be a probe to investigate the antiferromagnetic layer as it partly reflects the magnetic state of the antiferromagnet. In this work, we investigated the modulation of the exchange bias by a flow of electric current in Pt/Fe50Mn50/FeNi and Cu/Fe50Mn50/FeNi. We show that the exchange bias can be modulated just by applying the current due to interplay among the Joule heating, Ampere field, and current-induced effective field. (C) 2016 The Japan Society of Applied Physics

    DOI: 10.7567/JJAP.55.070304

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  110. Switching local magnetization by electric-field-induced domain wall motion Reviewed

    Haruka Kakizakai, Fuyuki Ando, Tomohiro Koyama, Kihiro Yamada, Masashi Kawaguchi, Sanghoon Kim, Kab-Jin Kim, Takahiro Moriyama, Daichi Chiba, Teruo Ono

    APPLIED PHYSICS EXPRESS   Vol. 9 ( 6 )   2016.6

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    Electric field effect on magnetism is an appealing technique for manipulating magnetization at a low energy cost. Here, we show that the local magnetization of an ultrathin Co film can be switched by simply applying a gate electric field without the assistance of any external magnetic field or current flow. The local magnetization switching is explained by nucleation and annihilation of magnetic domains through domain wall motion induced by the electric field. Our results lead to external-field-free and ultralow-energy spintronic applications. (C) 2016 The Japan Society of Applied Physics

    DOI: 10.7567/APEX.9.063004

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  111. Observation of magnon Hall-like effect for sample-edge scattering in unsaturated YIG Reviewed

    Kenji Tanabe, Ryo Matsumoto, Jun-Ichiro Ohe, Shuichi Murakami, Takahiro Moriyama, Daichi Chiba, Kensuke Kobayashi, Teruo Ono

    PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS   Vol. 253 ( 4 ) page: 783 - 787   2016.4

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    We report the observation of a magnon Hall-like effect for the scattering of magnons at the sample edge in Y3Fe5O12 crystals. The experiments are performed under an out-of-plane magnetic field at room temperature using an infrared thermometry. When the magnons are incident into the sample edge in the unsaturated magnetic structure, appreciable transverse thermal gradient is detected. This thermal gradient could be attributed to magnon Hall effect for sample-edge scattering. We unexpectedly find that this effect is largely enhanced in the unsaturated regime, compared with the saturated regime where theoretical mechanism of magnon Hall effect due to the Berry curvature has been proposed previously.

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  112. Observation of asymmetry in domain wall velocity under transverse magnetic field Reviewed

    K. -J. Kim, Y. Yoshimura, T. Okuno, T. Moriyama, S. -W. Lee, K. -J. Lee, Y. Nakatani, T. Ono

    APL MATERIALS   Vol. 4 ( 3 )   2016.3

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    The dynamics of a magnetic domain wall (DW) under a transverse magnetic field H-y are investigated in two-dimensional (2D) Co/Ni microstrips, where an interfacial Dzyaloshinskii-Moriya interaction (DMI) exists with DMI vector D lying in +y direction. The DW velocity exhibits asymmetric behavior for +/- H-y; that is, the DW velocity becomes faster when H-y is applied antiparallel to D. The key experimental results are reproduced in a 2D micromagnetic simulation, which reveals that the interfacial DMI suppresses the periodic change of the average DW angle phi even above the Walker breakdown and that H-y changes phi, resulting in a velocity asymmetry. This suggests that the 2D DW motion, despite its microscopic complexity, simply depends on the average angle of the DW and thus can be described using a one-dimensional soliton model. These findings provide insight into the magnetic DW dynamics in 2D systems, which are important for emerging spin-orbitronic applications. (C) 2016 Author(s).

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  113. Anomalous behavior of 1/f noise in graphene near the charge neutrality point Reviewed

    Shunpei Takeshita, Sadashige Matsuo, Takahiro Tanaka, Shu Nakaharai, Kazuhito Tsukagoshi, Takahiro Moriyama, Teruo Ono, Tomonori Arakawa, Kensuke Kobayashi

    APPLIED PHYSICS LETTERS   Vol. 108 ( 10 )   2016.3

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    We investigate the noise in single layer graphene devices from equilibrium to far-from equilibrium and found that the 1/f noise shows an anomalous dependence on the source-drain bias voltage (V-SD). While the Hooge's relation is not the case around the charge neutrality point, we found that it is recovered at very low V-SD region. We propose that the depinning of the electron-hole puddles is induced at finite V-SD, which may explain this anomalous noise behavior. (C) 2016 AIP Publishing LLC.

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  114. Soliton-like magnetic domain wall motion induced by the interfacial Dzyaloshinskii-Moriya interaction Reviewed

    Yoko Yoshimura, Kab-Jin Kim, Takuya Taniguchi, Takayuki Tono, Kohei Ueda, Ryo Hiramatsu, Takahiro Moriyama, Keisuke Yamada, Yoshinobu Nakatani, Teruo Ono

    NATURE PHYSICS   Vol. 12 ( 2 ) page: 157 - +   2016.2

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    Topological defects such as magnetic solitons, vortices and skyrmions have started to play an important role in modern magnetism because of their extraordinary stability(1), which can be exploited in the production of memory devices. Recently, a type of antisymmetric exchange interaction, namely the Dzyaloshinskii-Moriya interaction (DMI; refs 2,3), has been uncovered and found to influence the formation of topological defects(4-7). Exploring how the DMI affects the dynamics of topological defects is therefore an important task. Here we investigate the dynamics of the magnetic domain wall (DW) under a DMI by developing a real time DW detection scheme. For a weak DMI, the DW velocity increases with the external field and reaches a peak velocity at a threshold field, beyond which it abruptly decreases. For a strong DMI, on the other hand, the velocity reduction is completely suppressed and the peak velocity is maintained constant even far above the threshold field. Such a distinct trend of the velocity can be explained in terms of a magnetic soliton, the topology of which is protected during its motion. Our results therefore shed light on the physics of dynamic topological defects, which paves the way for future work in topology-based memory applications.

    DOI: 10.1038/NPHYS3535

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  115. Atrial natriuretic peptide attenuation of renal ischemia-reperfusion injury after major surgery

    Takahiro Moriyama

    Journal of Surgical Research   Vol. 201 ( 1 ) page: 213 - 218   2016

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    DOI: 10.1016/J.JSS.2015.10.036

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  116. Comparison of three early biomarkers for acute kidney injury after cardiac surgery under cardiopulmonary bypass

    Takahiro Moriyama

    Journal of Intensive Care     2016

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    DOI: 10.1186/S40560-016-0164-1

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  117. Traveling surface spin-wave resonance spectroscopy using surface acoustic waves Reviewed

    P. G. Gowtham, T. Moriyama, D. C. Ralph, R. A. Buhrman

    JOURNAL OF APPLIED PHYSICS   Vol. 118 ( 23 )   2015.12

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    Coherent gigahertz-frequency surface acoustic waves (SAWs) traveling on the surface of a piezoelectric crystal can, via the magnetoelastic interaction, resonantly excite traveling surface spin waves in an adjacent thin-film ferromagnet. These excited surface spin waves, traveling with a definite in-plane wave-vector q(parallel to) enforced by the SAW, can be detected by measuring changes in the electro-acoustical transmission of a SAW delay line. Here, we provide a demonstration that such measurements constitute a precise and quantitative technique for spin-wave spectroscopy, providing a means to determine both isotropic and anisotropic contributions to the spin-wave dispersion and damping. We demonstrate the effectiveness of this spectroscopic technique by measuring the spin-wave properties of a Ni thin film for a large range of wave vectors, vertical bar q(parallel to)vertical bar = 2.5 x 10(4)-8 x 10(4) cm(-1), over which anisotropic dipolar interactions vary from being negligible to quite significant. (C) 2015 AIP Publishing LLC.

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  118. Spin motive force induced in Fe3O4 thin films with negative spin polarization Reviewed

    Masaki Nagata, Takahiro Moriyama, Kenji Tanabe, Kensho Tanaka, Daichi Chiba, Jun-ichiro Ohe, Yuki Hisamatsu, Tomohiko Niizeki, Hideto Yanagihara, Eiji Kita, Teruo Ono

    APPLIED PHYSICS EXPRESS   Vol. 8 ( 12 )   2015.12

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    Spin motive force (SMF) is induced by a time and spatial derivative of magnetizations and is dependent on spin polarization. We compare the SMF in FeNi with positive spin polarization with that in a magnetite (Fe3O4) with negative spin polarization. We observe the SMF induced by a nonuniform ferromagnetic resonance in Fe3O4 and find that the SMF in Fe3O4 is opposite to that in FeNi. This result originates from the negative spin polarization of Fe3O4. Our clear observation of the SMF depending on the sign of the spin polarization agrees well with the framework of the SMF theory. (C) 2015 The Japan Society of Applied Physics

    DOI: 10.7567/APEX.8.123001

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  119. Interfacial Dzyaloshinskii-Moriya interaction studied by time-resolved scanning Kerr microscopy Reviewed

    H. S. Koerner, J. Stigloher, H. G. Bauer, H. Hata, T. Taniguchi, T. Moriyama, T. Ono, C. H. Back

    PHYSICAL REVIEW B   Vol. 92 ( 22 )   2015.12

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    We investigate the influence of the interfacial Dzyaloshinskii-Moriya interaction (DMI) on the propagation of Damon-Eshbach spin waves in micrometer-sized Pt(2 nm)/Co(0.4 nm)/Py(5 nm)/MgO(5 nm) stripes. We use time-resolved scanning Kerr microscopy to image the spin waves excited by a microwave antenna and to directly access their dispersion. The presence of an interfacial DMI manifests itself in an asymmetry in the dispersion for counterpropagating spin waves which reverses sign upon reversal of the direction of the externally applied magnetic field. From this asymmetry we deduce the strength of the interfacial DMI. Micromagnetic simulations confirm that the observed difference in the wave numbers and the signature of the asymmetry are characteristic for the occurrence of an interfacial DMI at the Pt/Co interface and cannot be explained by the uniaxial perpendicular magnetic anisotropy field originating from the same interface.

    DOI: 10.1103/PhysRevB.92.220413

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  120. Sequential write-read operations in FeRh antiferromagnetic memory Reviewed

    Takahiro Moriyama, Noriko Matsuzaki, Kab-Jin Kim, Ippei Suzuki, Tomoyasu Taniyama, Teruo Ono

    APPLIED PHYSICS LETTERS   Vol. 107 ( 12 )   2015.9

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    B2-ordered FeRh has been known to exhibit antiferromagnetic-ferromagnetic (AF-F) phase transitions in the vicinity of room temperature. Manipulation of the Neel order via AF-F phase transition and recent experimental observation of the anisotropic magnetoresistance in antiferromagnetic FeRh has proven that FeRh is a promising candidate for antiferromagnetic memory material. In this work, we demonstrate sequential write and read operations in antiferromagnetic memory resistors made of B2-orderd FeRh thin films by a magnetic field and electric current only, which open a realistic pathway towards operational antiferromagnetic memory devices. (C) 2015 AIP Publishing LLC.

    DOI: 10.1063/1.4931567

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  121. Edge mixing dynamics in graphene p-n junctions in the quantum Hall regime Reviewed

    Sadashige Matsuo, Shunpei Takeshita, Takahiro Tanaka, Shu Nakaharai, Kazuhito Tsukagoshi, Takahiro Moriyama, Teruo Ono, Kensuke Kobayashi

    NATURE COMMUNICATIONS   Vol. 6   2015.9

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    Massless Dirac electron systems such as graphene exhibit a distinct half-integer quantum Hall effect, and in the bipolar transport regime co-propagating edge states along the p-n junction are realized. Additionally, these edge states are uniformly mixed at the junction, which makes it a unique structure to partition electrons in these edge states. Although many experimental works have addressed this issue, the microscopic dynamics of electron partition in this peculiar structure remains unclear. Here we performed shot-noise measurements on the junction in the quantum Hall regime as well as at zero magnetic field. We found that, in sharp contrast with the zero-field case, the shot noise in the quantum Hall regime is finite in the bipolar regime, but is strongly suppressed in the unipolar regime. Our observation is consistent with the theoretical prediction and gives microscopic evidence that the edge states are uniquely mixed along the p-n junction.

    DOI: 10.1038/ncomms9066

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  122. Precise control of magnetic domain wall displacement by a nanosecond current pulse in Co/Ni nanowires Reviewed

    Takuya Taniguchi, Kab-Jin Kim, Takayuki Tono, Takahiro Moriyama, Yoshinobu Nakatani, Teruo Ono

    APPLIED PHYSICS EXPRESS   Vol. 8 ( 7 )   2015.7

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    Magnetic domain wall (DW) motion induced by nanosecond current pulses is investigated in Co/Ni nanowires where the DW motion is driven by either adiabatic spin transfer torque (STT) or spin Hall torque (SHT). The DW displacement, including transient displacement and steady-state displacement, is found to be linearly related to the current pulse duration for both current-induced torques. The transient displacement is found to be less than 10% of the DW displacement. This result implies that the DW position can be controlled by tuning the duration of the current pulse, which enables a robust operation of racetrack memory. (C) 2015 The Japan Society of Applied Physics

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  123. Ferromagnetic resonance measurements in sub-nanometer Fe films Reviewed

    Hayato Mizuno, Takahiro Moriyama, Masashi Kawaguchi, Masaki Nagata, Kensho Tanaka, Tomohiro Koyama, Daichi Chiba, Teruo Ono

    APPLIED PHYSICS EXPRESS   Vol. 8 ( 7 )   2015.7

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    We show that our ferromagnetic resonance (FMR) measurement based on the rectification effect is sufficiently sensitive for characterizing various static and dynamic magnetic properties of a sub-nanometer ferromagnetic film where the interfacial effects dominate. The extracted properties, such as the Lande g-factor, the effective demagnetizing field, and the Gilbert damping parameter, are reasonably well scaled with the film thickness, indicating that our measurements clearly capture the interfacial properties of the sub-nanometer-thick film. In particular, the capability of the g-factor extraction in the ultrathin film will be very helpful for characterizing the various interfacial effects involved with interfacial orbit moments and spin-orbit interactions. (C) 2015 The Japan Society of Applied Physics

    DOI: 10.7567/APEX.8.073003

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  124. Current induced antiferro-ferromagnetic transition in FeRh nanowires Reviewed

    Noriko Matsuzaki, Takahiro Moriyama, Masaki Nagata, Kab-Jin Kim, Ippei Suzuki, Tomoyasu Taniyama, Teruo Ono

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 54 ( 7 )   2015.7

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    We investigated the antiferromagnetic-ferromagnetic phase transition of FeRh nanowires induced by an electric current. The critical current I-cr for the phase transition decreases with increasing the sample temperature. It is found that the RcrIcr2, where R-cr is the resistance at I-cr, linearly decreases as the sample temperature increases, suggesting that the temperature raised by the Joule heating is responsible for the transition. We also studied for various wire widths to characterize the heat dissipation of the nanowires. Our results provide a way to explore the Joule heating in high density nanosized electrical devices where significant electric current flow is involved. (C) 2015 The Japan Society of Applied Physics

    DOI: 10.7567/JJAP.54.073002

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  125. Dimensional crossover characterized by distribution of magnetic domain wall creep velocity Reviewed

    Takuya Taniguchi, Kab-Jin Kim, Takayuki Tono, Sanghoon Kim, Takahiro Moriyama, Teruo Ono

    APPLIED PHYSICS EXPRESS   Vol. 8 ( 7 )   2015.7

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    We studied the magnetic domain wall (DW) creep motion in two driving forces: external magnetic field and spin Hall torque (SHT). The dimensional crossover from two to one dimension is identified by looking at the distribution width of the DW velocity depending on the wire width. The distribution widths are found to be similar regardless of the driving forces in narrow wires, whereas they show nonnegligible differences depending on the driving force in wide wires. Therefore, the dimensional crossover implies that the effective magnetic field induced by the SHT becomes equivalent to the external magnetic field only when the wire is considered as one-dimensional. (C) 2015 The Japan Society of Applied Physics

    DOI: 10.7567/APEX.8.073004

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  126. Chiral magnetic domain wall in ferrimagnetic GdFeCo wires Reviewed

    Takayuki Tono, Takuya Taniguchi, Kab-Jin Kim, Takahiro Moriyama, Arata Tsukamoto, Teruo Ono

    APPLIED PHYSICS EXPRESS   Vol. 8 ( 7 )   2015.7

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    Field-driven magnetic domain wall (DW) motion was investigated in ferrimagnetic GdFeCo wires with perpendicular magnetic anisotropy. The DW velocity as a function of the out-of-plane magnetic field exhibited the Walker breakdown phenomenon. The DW velocity was found to be significantly affected by the in-plane bias field: a minimum DW velocity was observed at a finite in-plane magnetic field (H-m), and the sign of H-m was found to reverse when the DW structure was changed from up-down-to down-up. These results imply that chiral DWs are formed in ferrimagnetic GdFeCo wires, despite their bulk and amorphous phase. (C) 2015 The Japan Society of Applied Physics

    DOI: 10.7567/APEX.8.073001

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  127. Antiferromagnet-mediated spin transfer between a metal and a ferromagnet Reviewed

    So Takei, Takahiro Moriyama, Teruo Ono, Yaroslav Tserkovnyak

    PHYSICAL REVIEW B   Vol. 92 ( 2 )   2015.7

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    We develop a theory for spin transported by coherent Neel dynamics through an antiferromagnetic insulator coupled to a ferromagnetic insulator on one side and a current-carrying normal metal with strong spin-orbit coupling on the other. The ferromagnet is considered within the monodomain limit and we assume its coupling to the local antiferromagnet Neel order at the ferromagnet vertical bar antiferromagnet interface through exchange coupling. Coupling between the charge current and the local Neel order at the other interface is described using spin Hall phenomenology. Spin transport through the antiferromagnet, assumed to possess an easy-axis magnetic anisotropy, is solved within the adiabatic approximation and the effect of spin current flowing into the ferromagnet on its resonance linewidth is evaluated. Onsager reciprocity is used to evaluate the inverse spin Hall voltage generated across the metal by a dynamic ferromagnet as a function the antiferromagnet thickness.

    DOI: 10.1103/PhysRevB.92.020409

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  128. Parity effect of bipolar quantum Hall edge transport around graphene antidots Reviewed

    Sadashige Matsuo, Shu Nakaharai, Katsuyoshi Komatsu, Kazuhito Tsukagoshi, Takahiro Moriyama, Teruo Ono, Kensuke Kobayashi

    SCIENTIFIC REPORTS   Vol. 5   2015.6

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    Parity effect, which means that even-odd property of an integer physical parameter results in an essential difference, ubiquitously appears and enables us to grasp its physical essence as the microscopic mechanism is less significant in coarse graining. Here we report a new parity effect of quantum Hall edge transport in graphene antidot devices with pn junctions (PNJs). We found and experimentally verified that the bipolar quantum Hall edge transport is drastically affected by the parity of the number of PNJs. This parity effect is universal in bipolar quantum Hall edge transport of not only graphene but also massless Dirac electron systems. These results offer a promising way to design electron interferometers in graphene.

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  129. Ferromagnetic resonance measurement using stroboscopic magneto-optical Kerr effect Reviewed

    Takahiro Moriyama, Seungha Yoon, Robert D. McMichael

    JOURNAL OF APPLIED PHYSICS   Vol. 117 ( 21 )   2015.6

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    We have developed a novel ferromagnetic resonance (FMR) measurement technique using the magneto-optical Kerr effect. The measurement technique uses microwave-frequency, intensitymodulated light to stroboscopically measure the Kerr angle due to the magnetization precession. We demonstrate that this stroboscopic magneto-optical Kerr effect provides a frequency domain and phase sensitive FMR measurement. The measurement is sensitive enough to detect the precessing magnetization with the precession cone angle below 1 degrees . (C) 2015 AIP Publishing LLC.

    DOI: 10.1063/1.4922126

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  130. Micro-focused Brillouin light scattering study of the magnetization dynamics driven by Spin Hall effect in a transversely magnetized NiFe nanowire Reviewed

    M. Madami, G. Gubbiotti, T. Moriyama, K. Tanaka, G. Siracusano, M. Carpentieri, G. Finocchio, S. Tacchi, T. Ono, G. Carlotti

    JOURNAL OF APPLIED PHYSICS   Vol. 117 ( 17 )   2015.5

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    We employed micro-focused Brillouin light scattering to study the amplification of the thermal spin wave eigenmodes by means of a pure spin current, generated by the spin-Hall effect, in a transversely magnetized Pt(4 nm)/NiFe(4 nm)/SiO2(5 nm) layered nanowire with lateral dimensions 500 x 2750 nm(2). The frequency and the cross section of both the center (fundamental) and the edge spin wave modes have been measured as a function of the intensity of the injected dc electric current. The frequency of both modes exhibits a clear redshift while their cross section is greatly enhanced on increasing the intensity of the injected dc. A threshold-like behavior is observed for a value of the injected dc of 2.8 mA. Interestingly, an additional mode, localized in the central part of the nanowire, appears at higher frequency on increasing the intensity of the injected dc above the threshold value. Micromagnetic simulations were used to quantitatively reproduce the experimental results and to investigate the complex non-linear dynamics induced by the spin-Hall effect, including the modification of the spatial profile of the spin wave modes and the appearance of the extra mode above the threshold. (C) 2015 AIP Publishing LLC.

    DOI: 10.1063/1.4907612

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  131. Layer thickness dependence of current induced effective fields in ferromagnetic multilayers Reviewed

    M. Kawaguchi, T. Moriyama, T. Koyama, D. Chiba, T. Ono

    JOURNAL OF APPLIED PHYSICS   Vol. 117 ( 17 )   2015.5

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    We report the relation between current induced effective fields and ferromagnetic layer thickness. Hall measurements with rotating magnetic field show that the transverse and perpendicular effective fields have linear relations to the inverse of the magnetic moment m per area S. The results imply that both of these effective fields may originate from spin angular momentum transferring. However, the non-zero intercept of the transverse field at m/S = 0 implies that magnetization independent effects, such as Rashba effect, may contribute to transverse field. (C) 2015 AIP Publishing LLC.

    DOI: 10.1063/1.4914897

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  132. Anti-damping spin transfer torque through epitaxial nickel oxide Reviewed

    Takahiro Moriyama, So Takei, Masaki Nagata, Yoko Yoshimura, Noriko Matsuzaki, Takahito Terashima, Yaroslav Tserkovnyak, Teruo Ono

    APPLIED PHYSICS LETTERS   Vol. 106 ( 16 )   2015.4

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    We prepare the high quality epitaxial MgO(001)[100]/Pt(001)[100]/NiO(001)[100]/FeNi/SiO2 films to investigate the spin transport in the NiO antiferromagnetic insulator. The ferromagnetic resonance measurements of the FeNi under a spin current injection from the Pt by the spin Hall effect revealed the change of the ferromagnetic resonance linewidth depending on the amount of the spin current injection. The results can be interpreted that there is an angular momentum transfer through the NiO. A high efficient angular momentum transfer we observed in the epitaxial NiO can be attributed to the well-defined orientation of the antiferromagnetic moments and the spin quantization axis of the injected spin current. (C) 2015 AIP Publishing LLC.

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  133. Temperature dependence of current-induced magnetic domain wall motion in an asymmetric Co/Ni nanowire Reviewed

    Kohei Ueda, Ryo Hiramatsu, Kab-Jin Kim, Takuya Taniguchi, Takayuki Tono, Takahiro Moriyama, Teruo Ono

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 54 ( 3 ) page: 1 - 38004   2015.3

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    We have investigated the temperature dependence of current-induced magnetic domain wall (DW) motion in a Co/Ni nanowire, where the spin Hall torque is responsible for the DW motion. The threshold current density (J(th)) for DW motion is found to be dependent on the temperature T and the depinning magnetic field H-dep, which is different from the symmetric Co/Ni system where J(th) is insensitive to T and H-dep. This result indicates that an extrinsic pinning governs the DW motion when it is driven by the spin Hall torque. Our work therefore suggests that reducing the extrinsic pinning is a key for achieving a low-power-consumption device. (C) 2015 The Japan Society of Applied Physics

    DOI: 10.7567/JJAP.54.038004

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  134. Localized precessional mode of domain wall controlled by magnetic field and dc current Reviewed

    Ryo Hiramatsu, Kab-Jin Kim, Takuya Taniguchi, Takayuki Tono, Takahiro Moriyama, Shunsuke Fukami, Michihiko Yamanouchi, Hideo Ohno, Yoshinobu Nakatani, Teruo Ono

    APPLIED PHYSICS EXPRESS   Vol. 8 ( 2 ) page: 1 - 23003   2015.2

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    We present evidence of a localized magnetic domain-wall (DW) oscillator in Co/Ni nanowires. It is found that a DW is localized by the simultaneous application of a high magnetic field larger than the depinning field and a dc current smaller than the threshold current. A one-dimensional model and micromagnetic simulation reveal that the localized DW is in a precessional mode. Our results suggest that a localized magnetic DW oscillator can be realized by appropriately adjusting the magnetic field and dc current. (C) 2015 The Japan Society of Applied Physics

    DOI: 10.7567/APEX.8.023003

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  135. In-plane field-driven crossover in the spin-torque mechanism acting on magnetic domain walls in Co/Ni Reviewed

    Kohei Ueda, Kab-Jin Kim, Takuya Taniguchi, Takayuki Tono, Takahiro Moriyama, Teruo Ono

    PHYSICAL REVIEW B   Vol. 91 ( 6 )   2015.2

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    We investigate the in-plane field dependence of current-induced magnetic domain wall motion in asymmetric Co/Ninano wires. The application of an in-plane field changed the direction of domain wall motion. In a systematic study, by varying the magnetic layer thickness, we show that the in-plane field induces a crossover from spin Hall torque to adiabatic spin-transfer torque for the magnetic domain wall motion. Furthermore, the dependence of the threshold current density on the in-plane longitudinal field provides a way for determining the strength of the Dzyaloshinskii-Moriya interaction.

    DOI: 10.1103/PhysRevB.91.060405

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  136. Parity effect of bipolar quantum Hall edge transport around graphene antidots (5, 11723, 2015)

    Takahiro Moriyama

    Scientific Reports   Vol. 5   2015

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    DOI: 10.1038/SREP12591

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  137. Micromagnetic simulation of spin wave propagation in a ferromagnetic film with different thicknesses Reviewed

    Hiroshi Hata, Takahiro Moriyama, Kenji Tanabe, Kensuke Kobayashi, Ryo Matsumoto, Shuichi Murakami, Jun-ichiro Ohe, Daichi Chiba, Teruo Ono

    J. Magn. Soc. Jpn.   Vol. 39 ( 4 ) page: 151 - 155   2015

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    We have shown by micromagnetic simulation that the wavelength of the spin wave (SW) is modulated when the SW propagates across a step between two ferromagnetic films with different thicknesses. Since the wavelength of the SW depends on the film thickness, the thickness difference works as the different medium in Snell's law. The wavelength modulation obtained by the simulation showed a good agreement with Snell's law.

    DOI: 10.3379/msjmag.1506R004

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    Other Link: https://jlc.jst.go.jp/DN/JLC/20012933769?from=CiNii

  138. Effective method of continuous rocuronium administration based on effect-site concentrations using a pharmacokinetic/pharmacodynamic model during propofol-remifentanil anesthesia

    Takahiro Moriyama

    Journal of Anesthesia   Vol. 29 ( 4 ) page: 593 - 599   2015

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    DOI: 10.1007/S00540-015-1991-2

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  139. Room temperature write-read operations in antiferromagnetic memory

    Takahiro Moriyama

    ArXiv     2015

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  140. Proposal for quantifying the Dzyaloshinsky-Moriya interaction by domain walls annihilation measurement Reviewed

    Ryo Hiramatsu, Kab-Jin Kim, Yoshinobu Nakatani, Takahiro Moriyama, Teruo Ono

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 53 ( 10 )   2014.10

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    We show that the magnitude of the Dzyaloshinsky-Moriya interaction (DMI) can be determined by a field-driven domain-walls (DWs) annihilation measurement. It is predicted that the DMI induces antiparallel Neel DWs which form a metastable 360 degrees DW when they approach to each other. We find that an annihilation field, over which two DWs collide and vanish, is proportional to the magnitude of the DMI. This result suggests that the DMI can be quantified by a simple measurement of the annihilation field. (C) 2014 The Japan Society of Applied Physics

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  141. Linewidth broadening of optical precession mode in synthetic antiferromagnet Reviewed

    Kensho Tanaka, Takahiro Moriyama, Masaki Nagata, Takeshi Seki, Koki Takanashi, Saburo Takahashi, Teruo Ono

    APPLIED PHYSICS EXPRESS   Vol. 7 ( 6 ) page: 1 - 63010   2014.6

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    We investigate the magnetization dynamics in synthetic antiferromagnetic (SyAFM) Fe/[Co/Cu](10)/Co/Pt multilayers using the microwave rectifying effect. We observe two distinct resonant modes in the dynamics. Numerical simulations reveal that the resonant modes can be attributed to acoustic and optical modes, which are the characteristic resonant modes of antiferromagnetically coupled materials. It is found that the'linewidth of the optical mode is larger than that of the acoustic mode by a factor of 5. This broadening of the linewidth in the optical modes can be explained by the mutual spin pumping effect between the magnetizations precessing out of phase. (C) 2014 The Japan Society of Applied Physics

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  142. Transition in mechanism for current-driven magnetic domain wall dynamics Reviewed

    Kohei Ueda, Kab-Jin Kim, Yoko Yoshimura, Ryo Hiramatsu, Takahiro Moriyama, Daichi Chiba, Hironobu Tanigawa, Tetsuhiro Suzuki, Eiji Kariyada, Teruo Ono

    APPLIED PHYSICS EXPRESS   Vol. 7 ( 5 ) page: 1 - 53006   2014.5

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    We report a systematic study of the DW motion in perpendicularly magnetized Co/Ni nanowires having different thicknesses with structure inversion asymmetry. The transition from bulk to interfacial effects is confirmed as a change in the DW motion direction at a reduced layer thickness. The bias field dependence reveals that the adiabatic spin transfer torque (STT) dominates the DW motion in the thick regime, whereas the interfacial torque originating from the spin Hall effect (SHE) is responsible for the DW motion with a fixed DW chirality induced by the Dzyaloshinskii-Moriya interaction (DMI) in the thin regime. (C) 2014 The Japan Society of Applied Physics

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  143. Tradeoff between low-power operation and thermal stability in magnetic domain-wall-motion devices driven by spin Hall torque Reviewed

    Kab-Jin Kim, Ryo Hiramatsu, Takahiro Moriyama, Hironobu Tanigawa, Tetsuhiro Suzuki, Eiji Kariyada, Teruo Ono

    APPLIED PHYSICS EXPRESS   Vol. 7 ( 5 ) page: 1 - 53003   2014.5

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    We investigate the wire-width dependence of the critical current density for the motion of a magnetic domain wall (DW) in asymmetric Co/Ni nanowires, where spin Hall torque dominates the current-induced DW motion. It is found that both the critical current density for DW motion and the pinning field of a DW increase as the wire width decreases and that the critical current density for DW motion is proportional to the pinning field of the DW; this finding suggests a tradeoff between low-power operation and thermal stability in magnetic domain-wall-motion devices driven by spin Hall torque. (C) 2014 The Japan Society of Applied Physics

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  144. Real-time observation of Snell's law for spin waves in thin ferromagnetic films Reviewed

    Kenji Tanabe, Ryo Matsumoto, Jun-ichiro Ohe, Shuichi Murakami, Takahiro Moriyama, Daichi Chiba, Kensuke Kobayashi, Teruo Ono

    APPLIED PHYSICS EXPRESS   Vol. 7 ( 5 ) page: 1 - 53001   2014.5

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    We report the real-time observation of spin-wave propagation across a step inserted between two ferromagnetic films with different thicknesses. Because the dispersion relation of the spin wave depends on the thickness of the film, the step works as a junction to affect the spin wave propagation. When the spin wave transmits through the junction, the wavenumber undergoes modulation as per Snell's law, which states that the refraction index is proportional to the wavenumber. From the viewpoint of magnonics, the present achievement opens up new possibilities of controlling the wavenumber of spin waves. (C) 2014 The Japan Society of Applied Physics

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  145. Different stochastic behaviors for magnetic field and current in domain wall creep motion Reviewed

    Takuya Taniguchi, Kab-Jin Kim, Yoko Yoshimura, Takahiro Moriyama, Hironobu Tanigawa, Tetsuhiro Suzuki, Eiji Kariyada, Teruo Ono

    APPLIED PHYSICS EXPRESS   Vol. 7 ( 5 ) page: 1 - 53005   2014.5

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    Magnetic domain wall (DW) creep motions driven by a magnetic field and by the spin Hall (SH) torque are investigated in perpendicularly magnetized Co/Ni nanowires with structural inversion asymmetry. It is found that the DW arrival time distribution becomes wider when a DW is driven by the SH torque compared with that driven by a magnetic field. Our results indicate that the SH torque and a magnetic field drive a DW in different ways in the DW creep regime, although the SH torque is generally considered to induce an effective field. (C) 2014 The Japan Society of Applied Physics

    DOI: 10.7567/APEX.7.053005

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  146. Spin-wave-induced domain wall motion in perpendicularly magnetized system Reviewed

    Hiroshi Hata, Takuya Taniguchi, Hyun-Woo Lee, Takahiro Moriyama, Teruo Ono

    APPLIED PHYSICS EXPRESS   Vol. 7 ( 3 ) page: 1 - 33001   2014.3

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    Spin-wave (SW)-induced domain wall (DW) motion is investigated in a perpendicularly magnetized system by micromagnetic simulation. We particularly assume simulation parameters for Co/NI nanowires widely used in the experiment for spin-torque-driven DW motion. It is found that the domain wall moves toward the SW source in a broad frequency range, while it resonantly moves away from the SW source at certain frequencies. Our results indicate that the direction of the DW motion can be controlled by tuning the SW excitation frequency. (C) 2014 The Japan Society of Applied Physics

    DOI: 10.7567/APEX.7.033001

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  147. Effect of spin Hall torque on current-induced precessional domain wall motion Reviewed

    Yoko Yoshimura, Tomohiro Koyama, Daichi Chiba, Yoshinobu Nakatani, Shunsuke Fukami, Michihiko Yamanouchi, Hideo Ohno, Kab-Jin Kim, Takahiro Moriyama, Teruo Ono

    APPLIED PHYSICS EXPRESS   Vol. 7 ( 3 ) page: 1 - 33005   2014.3

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    Two important mechanisms for current-induced domain wall (DW) dynamics, namely, precessional DW motion driven by the adiabatic spin transfer torque and steady DW motion induced by the spin Hall torque, have been proposed and experimentally confirmed. However, the effect of the spin Hall torque on precessional DW motion has not been reported yet. Here, we show that the spin Hall torque affects the precessional DW motion when the in-plane field is applied. It is found that the in-plane field induces a half rotation time difference during DW precession, which gives rise to the nonvanishing spin Hall torque on the precessional DW motion. (C) 2014 The Japan Society of Applied Physics

    DOI: 10.7567/APEX.7.033005

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  148. Ferromagnetic Resonance in Magnetite Thin Films Reviewed

    Masaki Nagata, Kenji Tanabe, Takahiro Moriyama, Daichi Chiba, Jun-Ichiro Ohe, Makoto Myoka, Tomohiko Niizeki, Hideto Yanagihara, Eiji Kita, Teruo Ono

    IEEE TRANSACTIONS ON MAGNETICS   Vol. 50 ( 1 ) page: 1400203-1 - 1400203-3   2014.1

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    We have been investigating the spin motive force induced by magnetization dynamics in ferromagnetic materials. Ferrimagnetic materials are expected to exhibit even larger spin motive force due to their spatially staggered magnetic structure and high frequency spin wave modes. We believe that magnetite (Fe3O4) is one of the candidates for this purpose. Here, we report magnetic resonance in Fe3O4 thin films epitaxially grown on a MgO (001) substrate. The gyromagnetic ratio and the effective saturation magnetization are estimated to be 1.71 x 10(11) s(-1)T(-1) and 364 emu/cm(3), respectively. The Gilbert damping constant of 0.02 is obtained from the magnetic field dependence of the linewidth. We expect to investigate the spin motive force induced from this magnetic resonance.

    DOI: 10.1109/TMAG.2013.2274270

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  149. Current-Induced Effective Fields Detected by Magnetotrasport Measurements Reviewed

    Masashi Kawaguchi, Kazutoshi Shimamura, Shunsuke Fukami, Fumihiro Matsukura, Hideo Ohno, Takahiro Moriyama, Daichi Chiba, Teruo Ono

    APPLIED PHYSICS EXPRESS   Vol. 6 ( 11 ) page: 1 - 113002   2013.11

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    We show that the angle-dependent Hall measurement is an effective method to determine the current-induced effective fields by investigating MgO/Fe/Ta and MgO/Fe/Pt/Ta multilayer structures. The experimentally obtained Hall resistance under a relatively large dc electrical current is well described by considering two components of current-induced effective fields, which may be related to the spin Hall effect and the Rashba effect. The directions of the effective fields are consistent with and their magnitudes are comparable to those reported previously for similar multilayer structures. (C) 2013 The Japan Society of Applied Physics

    DOI: 10.7567/APEX.6.113002

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  150. Injection locking at zero field in two free layer spin-valves Reviewed

    Mario Carpentieri, Takahiro Moriyama, Bruno Azzerboni, Giovanni Finocchio

    Applied Physics Letters   Vol. 102 ( 10 )   2013.3

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    This paper predicts the possibility to achieve synchronization (via injection locking to a microwave current) of spin-transfer torque oscillators based on hybrid spin-valves composed by two free layers and two perpendicular polarizers at zero bias field. The locking regions are attained for microwave frequency near 0.5f0, f0, and 2f0, where f 0 is the input oscillator frequency. Those properties make this system promising for applications, such as high-speed frequency dividers and multipliers, and phase-locked-loop demodulators. © 2013 American Institute of Physics.

    DOI: 10.1063/1.4795597

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  151. Current-Induced Magnetic Domain Wall Motion in a Co/Ni Nanowire with Structural Inversion Asymmetry Reviewed

    Tomohiro Koyama, Hiroshi Hata, Kab-Jin Kim, Takahiro Moriyama, Hironobu Tanigawa, Tetsuhiro Suzuki, Yoshinobu Nakatani, Daichi Chiba, Teruo Ono

    APPLIED PHYSICS EXPRESS   Vol. 6 ( 3 ) page: 1 - 33001   2013.3

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    The authors have investigated the current-induced magnetic domain wall (DW) motion in perpendicularly magnetized Co/Ni nanowire with structural inversion asymmetry (SIA). In this system, DW motion to the direction of electric current flow, not electron flow, and high DW velocity up to 110 m/s were confirmed, which have never been observed in Co/Ni systems without SIA. In addition, we found that the DW velocity showed a strong dependence on the perpendicular magnetic field in the range of +/- 100 Oe. These results suggest that DW in the Co/Ni nanowire with SIA moves in the steady mode, not in the precessional mode. (C) 2013 The Japan Society of Applied Physics

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  152. High Spin Torque Efficiency of Magnetic Tunnel Junctions with MgO/CoFeB/MgO Free Layer Reviewed

    Guenole Jan, Yu-Jen Wang, Takahiro Moriyama, Yuan-Jen Lee, Mark Lin, Tom Zhong, Ru-Ying Tong, Terry Torng, Po-Kang Wang

    APPLIED PHYSICS EXPRESS   Vol. 5 ( 9 ) page: 1 - 93008   2012.9

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    We present the results of a perpendicular magnetic tunnel junction (MTJ) that displays simultaneously low critical switching current and voltage, as well as high thermal stability factor. These results were achieved using a free layer of the MgO/CoFeB/MgO structure by increasing the spin torque efficiency to an average of 3.0 k(B) T/mu A for 37-nm-diameter junctions, about three times that of a MgO/CoFeB/Ta free layer, which makes it the highest value reported to date. By comparing two films with different RA, hence different switching voltage and power, we explore the contributions of heating and voltage-modulated anisotropy change to the switching properties. (C) 2012 The Japan Society of Applied Physics

    DOI: 10.1143/APEX.5.093008

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  153. Phase locking and frequency doubling in spin-transfer-torque oscillators with two coupled free layers Reviewed

    Takahiro Moriyama, Giovanni Finocchio, Mario Carpentieri, Bruno Azzerboni, Daniel C. Ralph, Robert A. Buhrman

    PHYSICAL REVIEW B   Vol. 86 ( 6 ) page: 1 - 60411   2012.8

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    We report measurements of spin-torque-driven oscillations in magnetic multilayer devices containing two in-plane-oriented free layers designed to have significant coupling between them. They are driven to oscillate by spin-transfer torque from two perpendicularly oriented polarizers. For both measured devices and micromagnetic simulations, we find that the oscillations in the two free layers are phase locked, resulting in a frequency doubling and large output signals. The simulations suggest that the oscillations are due to spatially nonuniform dynamics characterized by coupled large-amplitude motion of the two free layers.

    DOI: 10.1103/PhysRevB.86.060411

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  154. Spin-transfer torque in nanoscale magnetic devices Reviewed

    D. C. Ralph, Y. -T. Cui, L. Q. Liu, T. Moriyama, C. Wang, R. A. Buhrman

    PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES   Vol. 369 ( 1951 ) page: 3617 - 3630   2011.9

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    We discuss recent highlights from research at Cornell University, Ithaca, New York, regarding the use of spin-transfer torques to control magnetic moments in nanoscale ferromagnetic devices. We highlight progress on reducing the critical currents necessary to produce spin-torque-driven magnetic switching, quantitative measurements of the magnitude and direction of the spin torque in magnetic tunnel junctions, and single-shot measurements of the magnetic dynamics generated during thermally assisted spin-torque switching.

    DOI: 10.1098/rsta.2011.0169

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  155. On-Chip Detection of Magnetic Dynamics for Single Microscopic Magnetic Dot Reviewed

    Xin Fan, Yaping Zhang, Xiaoming Kou, Rong Cao, Takahiro Moriyama, Huaiwu Zhang, John Q. Xiao

    IEEE TRANSACTIONS ON MAGNETICS   Vol. 47 ( 2 ) page: 359 - 361   2011.2

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    An inductive-based detection method of ferromagnetic resonance spectrum is demonstrated. For a single microscopic (similar to 40 nm x 40 mu m x 60 mu m) magnetic dot, which is much smaller than the microwave wavelength, the change in the microwave transmission signal is as large as 15 dB when its magnetic permeability changes. This detection is several orders more sensitive than the conventional transmission line method. Further understanding and development of this concept may lead to a microscopic microwave permeability sensor.

    DOI: 10.1109/TMAG.2010.2087376

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  156. Spin-Torque Ferromagnetic Resonance Induced by the Spin Hall Effect Reviewed

    Luqiao Liu, Takahiro Moriyama, D. C. Ralph, R. A. Buhrman

    PHYSICAL REVIEW LETTERS   Vol. 106 ( 3 ) page: 1 - 36601   2011.1

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    We demonstrate that the spin Hall effect in a thin film with strong spin-orbit scattering can excite magnetic precession in an adjacent ferromagnetic film. The flow of alternating current through a Pt/NiFe bilayer generates an oscillating transverse spin current in the Pt, and the resultant transfer of spin angular momentum to the NiFe induces ferromagnetic resonance dynamics. The Oersted field from the current also generates a ferromagnetic resonance signal but with a different symmetry. The ratio of these two signals allows a quantitative determination of the spin current and the spin Hall angle.

    DOI: 10.1103/PhysRevLett.106.036601

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  157. Effects of a Novel Benzodiazepine Derivative, JM-1232(-), on Human Gastroepiploic Artery In Vitro

    Takahiro Moriyama

    Journal of Cardiothoracic and Vascular Anesthesia   Vol. 25 ( 1 ) page: 72 - 77   2011

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    DOI: 10.1053/J.JVCA.2010.03.013

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  158. Tunnel magnetoresistance and spin torque switching in MgO-based magnetic tunnel junctions with a Co/Ni multilayer electrode Reviewed

    Takahiro Moriyama, Theodore J. Gudmundsen, Pinshane Y. Huang, Luqiao Liu, David A. Muller, Daniel C. Ralph, Robert A. Buhrman

    APPLIED PHYSICS LETTERS   Vol. 97 ( 7 ) page: 072513-1 - 072513-3   2010.8

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    We have fabricated MgO-barrier magnetic tunnel junctions with a Co/Ni switching layer to reduce the demagnetizing field via interface anisotropy. With a fcc-(111) oriented Co/Ni multilayer combined with an FeCoB insertion layer, the demagnetizing field is 2 kOe and the tunnel magnetoresistance can be as high as 106%. Room-temperature measurements of spin-torque switching are in good agreement with predictions for a reduced critical current associated with the small demagnetization for antiparallel-to-parallel switching. For parallel-to-antiparallel switching the small demagnetization field causes spatially nonuniform reversal nucleated at the sample ends, with a low energy barrier but a higher switching current. (C) 2010 American Institute of Physics. [doi:10.1063/1.3481798]

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  159. Spin-Polarized Transport and Dynamics in Magnetic Tunneling Structures Reviewed

    R. Cao, T. Moriyama, W. G. Wang, X. Fan, J. Kolodzey, S. H. Chen, C. R. Chang, Y. Tserkovnyak, B. K. Nikolic, J. Q. Xiao

    IEEE TRANSACTIONS ON MAGNETICS   Vol. 45 ( 10 ) page: 3434 - 3440   2009.10

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    In the first part of this paper, we report a systematic study on the structural evolution under rapid thermal annealing and the corresponding transport properties in magnetic tunnel junctions (MTJs) with a crystalline MgO barrier. The results clearly indicate that high tunneling magnetic resistance can be achieved by annealing MTJs at a very short time, and it is directly related to the formation of (001) crystalline structures. In the second part, we report the spin dynamics in tunneling structure through direct electrical detection. A surprisingly large voltage generation F/I/N and F/I/F in and junctions was observed, which is contradictory to the prediction from the standard spin-pumping theory. We proposed a theoretical formalism to study spin-pumping effects in ferromagnetic multilayer structures. The formalism can yield a remarkably clean physical picture of the spin and charge pumping in tunneling structures. The calculated values are consistent with experimental results.

    DOI: 10.1109/TMAG.2009.2024126

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  160. Magnetic tunnel junction based microwave detector Reviewed

    X. Fan, R. Cao, T. Moriyama, W. Wang, H. W. Zhang, John Q. Xiao

    APPLIED PHYSICS LETTERS   Vol. 95 ( 12 ) page: 122501   2009.9

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    We investigated the tunneling magnetoresistance change in magnetic tunnel junctions in the presence of external microwaves. The changing relative angle between the free layer and the pinned layer results in a rectification of the average resistance change. Due to its miniature size and its sensitivity to the microwave magnetic field, the magnetic tunnel junction could be utilized as a microwave power sensor with the ability to detect microwave frequencies. Studying microwave power and bias current dependencies reveals desired sensor features with linear responses and enhanced signal levels. (C) 2009 American Institute of Physics. [doi:10.1063/1.3231874]

    DOI: 10.1063/1.3231874

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  161. Ferromagnetic Resonance Spectroscopy With Very Large Precession Cone Angle in Magnetic Tunnel Junctions Reviewed

    T. Moriyama, X. Fan, Y. Q. Wen, H. W. Zhang, John Q. Xiao

    IEEE TRANSACTIONS ON MAGNETICS   Vol. 45 ( 5 ) page: 2047 - 2049   2009.5

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    We have developed an experimental technique to electrically characterize ferromagnetic resonance (FMR) with a large precession cone angle by using magnetic tunnel junctions on a coplanar waveguide. We observed FMR of a Ni(80)Fe(20) layer as the tunneling resistance change capturing the angle between the Ni(80)Fe(20) precession magnetization and a fixed magnetization in a reference electrode. The resonant frequency shifts with increasing microwave power as a result of the large precession cone angle that reduces the effective anisotropy field. We confirmed the validity of our results by the numerical simulations based on the Landau-Lifshitz-Gilbert equation.

    DOI: 10.1109/TMAG.2008.2002572

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  162. Nonlinear effective spin-mixing conductance in Pt/Ni80Fe20/Pt thin films Reviewed

    R. Cao, X. Fan, T. Moriyama, John Q. Xiao

    JOURNAL OF APPLIED PHYSICS   Vol. 105 ( 7 )   2009.4

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    In this study, the effective spin-mixing conductance in Ni80Fe20/Pt was investigated by measuring the interface-induced enhancement of the Gilbert damping constant. Ferromagnetic resonance spectra were measured in coplanar waveguide geometry with different incident microwave powers. The nonlinear behavior of normal Gilbert damping G(0) and effective spin-mixing conductance g.. have been observed when the incident microwave power is above a critical ac field h(rf) of 1.6 Oe. Both phenomena are explained by considering the coupling between spin coherent precession and spin wave modes. This work demonstrates the nonlinear behavior of the effective spin-mixing conductance g(up down arrow). It suggests that the nonlinear spin wave modes excited at high incident microwave power are detrimental to the spin pumping effect and should be avoided in future spin battery designs. The capability of tuning G0 and g(up down arrow) through the microwave power is also useful for the fundamental study on the damping mechanism. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3072443]

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  163. Modulation of P2X receptors in dorsal root ganglion neurons of streptozotocin-induced diabetic neuropathy

    Migita, K; Moriyama, T; Koguchi, M; Honda, K; Katsuragi, T; Takano, Y; Ueno, S

    NEUROSCIENCE LETTERS   Vol. 452 ( 2 ) page: 200 - 203   2009.3

  164. Reduction of the spin-torque critical current by partially canceling the free layer demagnetization field Reviewed

    Luqiao Liu, Takahiro Moriyama, D. C. Ralph, R. A. Buhrman

    APPLIED PHYSICS LETTERS   Vol. 94 ( 12 ) page: 122508   2009.3

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    We significantly reduce the critical current I(c0) for the onset of spin torque switching of the free layer in nanometer-scale in-plane magnetized spin valves by partially cancelling its intrinsic demagnetization field through the utilization of Co/Ni multilayer free layers. The out-of-plane magnetic anisotropy arising from the Co/Ni interfaces reduces the effective demagnetization field (H(eff)) while not significantly affecting the thermal stability of the free layer. A zero-thermal-fluctuation critical current density J(c0)similar to 2x10(6) A/cm(2) is determined through both current ramp rate and nanosecond pulse measurements, and comparisons with large H(eff) control samples confirm that this strategy is efficient in substantially decreasing I(c0).

    DOI: 10.1063/1.3107262

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  165. Spin dynamics in spintronic devices: A growing science in microwave applications Reviewed

    Xiao, J.Q., Cao, R., Moriyama, T., Fan, X., Wen, Q.-Y., Zhang, H.-W.

    Dianzi Keji Daxue Xuebao/Journal of the University of Electronic Science and Technology of China   Vol. 38 ( 5 ) page: 505 - 523   2009

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    DOI: 10.3969/j.issn.1001-0548.2009.05.004

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  166. INTRACELLULAR ALKALIZATION CAUSES PAIN SENSATION THROUGH ACTIVATION OF TRPA1

    Fujita, F; Uchida, K; Moriyama, T; Shima, A; Shibasaki, K; Inada, H; Sokabe, T; Tominaga, M

    JOURNAL OF PHYSIOLOGICAL SCIENCES   Vol. 59   page: 81 - 81   2009

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  167. Tunnel-barrier-enhanced dc voltage signals induced by magnetization dynamics in magnetic tunnel junctions Reviewed

    Yaroslav Tserkovnyak, T. Moriyama, John Q. Xiao

    PHYSICAL REVIEW B   Vol. 78 ( 2 ) page: 1 - 20401   2008.7

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    We theoretically study the recently observed tunnel-barrier-enhanced dc voltage signals generated by magnetization precession in magnetic tunnel junctions. While the spin pumping is suppressed by the high tunneling impedance, two complementary processes are predicted to result in a sizable voltage generation in ferromagnet (F)vertical bar insulator (I)vertical bar normal metal (N) and F vertical bar I vertical bar F junctions with one ferromagnet being resonantly excited. Magnetic dynamics in F vertical bar I vertical bar F systems induce a robust charge pumping, translating into voltage in open circuits. In addition, dynamics in a single ferromagnetic layer develop longitudinal spin accumulation inside the ferromagnet. A tunnel barrier then acts as a nonintrusive probe that converts the spin accumulation into a measurable voltage. Neither of the proposed mechanisms suffers from spin relaxation, which is typically fast on the scale of the exponentially slow tunneling rates. The longitudinal spin-accumulation buildup, however, is very sensitive to the phenomenological ingredients of the spin-relaxation picture.

    DOI: 10.1103/PhysRevB.78.020401

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  168. Real-time evolution of tunneling magnetoresistance during annealing in CoFeB/MgO/CoFeB magnetic tunnel junctions Reviewed

    W. G. Wang, C. Ni, A. Rumaiz, Y. Wang, X. Fan, T. Moriyama, R. Cao, Q. Y. Wen, H. W. Zhang, John Q. Xiao

    APPLIED PHYSICS LETTERS   Vol. 92 ( 15 ) page: 152501-1 - 152051-3   2008.4

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    We report the study of the real-time evolution of tunneling magnetoresistance (TMR) in CoFeB/MgO/CoFeB junctions during annealing at 380 degrees C. The TMR quickly developed at the early stage of the annealing, with 200% magnetoresistance observed in less than 10 min, followed by a slow approach to saturation. This evolution of TMR was correlated with the structural changes, including crystallization of amorphous CoFeB electrodes and improvement of barrier quality during the annealing. (c) 2008 American Institute of Physics.

    DOI: 10.1063/1.2903147

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  169. Magnetization reversal by microwave in magnetic tunnel junctions Reviewed

    T. Moriyama, R. Cao, John Q. Xiao, J. Lu, X. R. Wang, Q. Wen, H. W. Zhang

    JOURNAL OF APPLIED PHYSICS   Vol. 103 ( 7 )   2008.4

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    Microwave assisted magnetization switching was investigated using Fe(30)Co(70)/Al(2)O(3)/Ni(80)Fe(20) magnetic tunnel junctions incorporated with a coplanar waveguide. Coercivity reduction (or switching field) of Ni(80)Fe(20) layer was reduced with a microwave excitation. It was found that the coercivity reduction depends on both frequency and power of the microwave. The numerical simulation based on the Landau-Lifshitz-Gilbert equation reproduced the trend of the experimental data. The results indicate that microwave can be an efficient mean to switch the magnetization of a thin film.

    DOI: 10.1063/1.2838290

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  170. Microstructure, magnetic, and spin-dependent transport properties of (Zn,Cr)Te films fabricated by magnetron sputtering Reviewed

    W. G. Wang, K. J. Yee, D. H. Kim, K. J. Han, X. R. Wang, C. Ni, T. Moriyama, A. Mathew, R. Opila, T. Zhu, John Q. Xiao

    PHYSICAL REVIEW B   Vol. 77 ( 15 ) page: 1 - 155207   2008.4

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    Chromium doped zinc telluride thin films with various doping concentrations are fabricated by magnetron sputtering. These films are ferromagnetic and the Curie temperature increases with Cr concentration. X-ray diffraction, transmission electron microscopy, and magnetic circular dichroism characterizations show that the films are free of Cr1-xTex impurities and the ferromagnetism is intrinsic. The transport study shows that the resistivity and magnetoresistance are governed by variable range hopping at low temperatures. A negative magnetoresistance as large as -57% is observed at 5 K. The magnetoresistance and its temperature dependence can be well explained by a model involving an increase in the localization length of carriers with a magnetic field in the hopping region. An anomalous Hall effect is also observed and a possible origin of the sign difference between the anomalous Hall resistance and ordinary Hall resistance is discussed.

    DOI: 10.1103/PhysRevB.77.155207

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  171. Tunnel barrier enhanced voltage signal generated by magnetization precession of a single ferromagnetic layer Reviewed

    T. Moriyama, R. Cao, X. Fan, G. Xuan, B. K. Nikolic, Y. Tserkovnyak, J. Kolodzey, John Q. Xiao

    PHYSICAL REVIEW LETTERS   Vol. 100 ( 6 ) page: 1 - 67602   2008.2

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    We report the electrical detection of magnetization dynamics in an Al/AlO(x)/Ni(80)Fe(20)/Cu tunnel junction, where a Ni(80)Fe(20) ferromagnetic layer is brought into precession under ferromagnetic resonance conditions. The dc voltage generated across the junction by the precessing ferromagnet is enhanced about an order of magnitude compared to the voltage signal observed when the contacts in this type of multilayered structure are Ohmic. We discuss the relation of this phenomenon to magnetic spin pumping and speculate on other possible underlying mechanisms responsible for the enhanced electrical signal.

    DOI: 10.1103/PhysRevLett.100.067602

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  172. The effect of amino-acid infusion during off-pump coronary arterial bypass surgery on thermogenic and hormonal regulation

    Takahiro Moriyama

    Journal of Anesthesia   Vol. 22 ( 4 ) page: 354 - 360   2008

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    DOI: 10.1007/S00540-008-0651-1

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  173. Microwave-assisted magnetization switching of Ni80Fe20 in magnetic tunnel junctions Reviewed

    T. Moriyama, R. Cao, John Q. Xiao, J. Lu, X. R. Wang, Q. Wen, H. W. Zhang

    APPLIED PHYSICS LETTERS   Vol. 90 ( 15 ) page: 152503-1 - 152503-3   2007.4

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    Microwave-assisted magnetization switching was investigated using Fe30Co70/AlOx/Ni80Fe20 magnetic tunnel junctions incorporated with a coplanar waveguide. Coercivity field of Ni80Fe20 layer was dramatically reduced in a small amplitude microwave. The authors eliminated the thermal effect in coercivity reduction by comparing two types of measurements which are with and without spin precession in the presence of microwave. It was found that the coercivity reduction depends on both frequency and power of the microwave. The numerical simulation based on Landau-Lifshitz-Gilbert equation reproduced the trend of the experimental data. The results indicate that microwave can be an efficient means to switch the magnetization of a thin film. (c) 2007 American Institute of Physics.

    DOI: 10.1063/1.2720746

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  174. Direct measurement of barrier asymmetry in AlOx/ZrOy magnetic tunnel junctions using off-axis electron holography Reviewed

    Yu-Zi Liu, W. G. Wang, T. Moriyama, John Q. Xiao, Z. Zhang

    PHYSICAL REVIEW B   Vol. 75 ( 13 ) page: 1 - 134420   2007.4

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    Off-axis electron holography was used to investigate the barrier profile of the Py/AlOx/ZrOy/Py magnetic tunnel junctions with different ZrOy thicknesses. The tunneling magnetoresistance (TMR) has a strong dependence on bias voltage and the bias voltage for maximum TMR is shifted from zero. This shift increases with ZrOy barrier thickness due to the increasing barrier asymmetry in the junctions. The evolution of barrier asymmetry was directly observed by the phase change of the off-axis electron holography, which unambiguously shows the barrier profile changes from triangular to trapezoidal shape as increasing of ZrOy thickness.

    DOI: 10.1103/PhysRevB.75.134420

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  175. In vitro heating with polyethylene glycol coated Fe nanoparticles Reviewed

    M. J. Bonder, B. Srinivasan, G. Poirier, T. Moriyama, K. L. Kiick, G. C. Hadjipanayis

    IEEE TRANSACTIONS ON MAGNETICS   Vol. 42 ( 10 ) page: 3602 - 3604   2006.10

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    Magnetic nanoparticles coated with a biocompatible polymer are potential candidates for biomedical applications associated with the detection and treatment of cancer. By varying the length of a reaction tube, the nanoparticle size increases from 10 to 30 nm with a 1-3 nm carboxyl terminated polyethylene glycol (cPEG) coating. The saturation magnetization for all samples is greater than 100 emu/g. By increasing the length of the reaction tube there is an incorporation of an amorphous phase. Subjecting samples to a 4 Oe magnetic field oscillating at 500 kHz there are two characteristic temperatures depending on particle size. The temperature measured for larger particles saturates with time to 35 degrees C. Below a critical nanoparticle size the temperature reached exceeds 50 degrees C within the same timeframe.

    DOI: 10.1109/TMAG.2006.879075

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  176. Tunneling magnetoresistance in (001)-oriented FeCo/MgO/FeCo magnetic tunneling junctions grown by sputtering deposition Reviewed

    T Moriyama, C Ni, WG Wang, Zhang, X, JQ Xiao

    APPLIED PHYSICS LETTERS   Vol. 88 ( 22 )   2006.5

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    Magnetic tunneling junctions (MTJs) with MgO tunnel barrier have been fabricated on both oriented and nonoriented buffer layers on Si(001) substrate by magnetron sputtering. FeCo/MgO/FeCo MTJs fabricated on oriented buffer layers show larger tunneling magnetoresistance (TMR) value up to 84% without high temperature postannealing, whereas those MTJs on nonoriented buffer layers show 45% of TMR. The high-resolution transmission electron microscopy images reveal an excellent morphology and very coherent crystal structure with FeCo(001)[110]/MgO(001)x[100]/FeCo(001)[110] orientation. The results indicate that high TMR can be achieved without high temperature postannealing by sputtering deposition on appropriate oriented buffer layers. (c) 2006 American Institute of Physics.

    DOI: 10.1063/1.2207835

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  177. Spin-polarized transport in hybrid (Zn,Cr)Te/Al2O3/Co magnetic tunnel junctions Reviewed

    W. G. Wang, C. Ni, T. Moriyama, J. Wan, E. Nowak, John Q. Xiao

    APPLIED PHYSICS LETTERS   Vol. 88 ( 20 )   2006.5

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    Tunnel magnetoresistance (TMR) of 21% is observed at low temperature in hybrid magnetic tunnel junctions (MTJs) composed of a magnetic semiconductor (Zn,Cr)Te and Co electrodes separated by an alumina barrier. The TMR is observed up to 250 K, which is a considerable improvement over previous work on MTJs with semiconductor electrodes. The temperature and bias dependence of the TMR are consistent with a transport model involving spin-polarized tunneling and spin-independent hopping through impurity states.

    DOI: 10.1063/1.2205177

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  178. Magnetic tunnel junctions with L1(0)-ordered FePt alloy electrodes Reviewed

    T Moriyama, S Mitani, T Seki, T Shima, K Takanashi, A Sakuma

    JOURNAL OF APPLIED PHYSICS   Vol. 95 ( 11 ) page: 6789 - 6791   2004.6

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    Magnetic tunnel junctions (MTJs) with L1(0)-ordered FePt alloy electrodes were prepared on MgO(110) substrates, and structure and magnetotransport properties of the MTJs have been investigated. Tunnel magnetoresistance (TMR) of 34% is observed at 77 K for a junction with the FePt alloy electrode in which the degree of chemical order S is estimated to be similar to0.7. From S dependence of TMR in the MTJs, it is suggested that the spin polarization of FePt alloy electrodes increases with chemical ordering, which is consistent with first principles band structure calculations. (C) 2004 American Institute of Physics.

    DOI: 10.1063/1.1669212

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  179. Fe/MgO/FeCo(100) epitaxial magnetic tunnel junctions prepared by using in situ plasma oxidation Reviewed

    S Mitani, T Moriyama, K Takanashi

    JOURNAL OF APPLIED PHYSICS   Vol. 93 ( 10 ) page: 8041 - 8043   2003.5

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    Fe/MgO/FeCo epitaxial magnetic tunnel junctions (MTJs) were prepared on MgO(100) single crystal substrates by using in situ plasma oxidation for the formation of MgO barriers. The epitaxial relationship of Fe(001)/MgO(001)/FeCo(001) and Fe[100]//MgO[110]//FeCo[100] in the junctions was observed by reflection high-energy electron diffraction. Tunneling transport was clearly observed at low temperatures below about 150 K, and the barrier height of MgO is estimated to be 0.9 eV, which is smaller than the value expected from half of the band gap of bulk MgO. Tunnel magnetoresistance of 23% and 20% was observed at 4.2 and 77 K, respectively. The results suggest that plasma oxidation is useful for fabricating epitaxial magnetic tunnel junctions. (C) 2003 American Institute of Physics.

    DOI: 10.1063/1.1557338

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  180. Structure and tunnel magnetoresistance in Fe/MgF2/Co junctions with an oxide seed layer on an Fe bottom electrode Reviewed

    S Mitani, T Moriyama, K Takanashi

    JOURNAL OF APPLIED PHYSICS   Vol. 91 ( 10 ) page: 7200 - 7202   2002.5

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    Fe/MgF2/Co magnetic tunnel junctions (MTJs) with an oxide seed layer (MgO, Fe-O) inserted between an Fe bottom electrode and a MgF2 barrier layer have been prepared through the use of molecular beam epitaxy, and the effects of the seed layers on structure of subsequently deposited MgF2 barrier layers and tunnel magnetoresistance (TMR) have been investigated. The crystallographic orientation of MgF2 layers depends significantly on the seed layers, and furthermore, it has been found that the surface roughness of MgF2 layer is reduced by inserting a MgO seed layer. In Fe/MgF2 (3-12 nm)/Co MTJs without any seed layer, top Fe and bottom Co electrodes contact each other through pin holes in MgF2 layers. On the other hand, however, Fe and Co electrodes are separated both magnetically and electrically in Fe/MgO (0.3-0.5 nm)/MgF2 (2-5 nm)/Co MTJs, i.e., MgF2-based MTJs have successfully been prepared by inserting a thin MgO seed layer, resulting in TMR of about 10% observed at 4.2 K. (C) 2002 American Institute of Physics.

    DOI: 10.1063/1.1452200

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  181. Tunnel Magnetoresistance in Fe/MgO/MgF2/Co Junctions Reviewed

    T. Moriyama, S. Mitani, K. Takanashi

    Journal of the Magnetics Society of Japan   Vol. 26 ( 4 ) page: 405 - 409   2002

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    Ferromagnetic tunnel junctions (MTJs) in which a thin MgO seed layer was inserted between Fe bottom electrode and MgF<sub>2</sub> insulating barrier were fabricated through the use of molecular beam epitaxy. The structure and tunnel magnetoresistance (TMR) were investigated for Fe (200Å)/MgO (5Å)/MgF<sub>2</sub> (20Å)/Co (200Å) junctions. RHEED observation suggested that an MgF<sub>2</sub> layer deposited at room temperature was in amorphous or nanocrystalline state. The TMR ratio observed for a typical MTJ with barrier height of 1.6 eV was 1.8 % at 4.2 K and decreased with increasing temperature, down to 0.7 % at 293 K. It was found that the bias dependence of TMR shows a strong asymmetric feature, in contrast to conventional MTJs with amorphous alumina barriers.

    DOI: 10.3379/jmsjmag.26.405

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MISC 8

  1. Antiferromagnetic Materials for High-speed spintronics Invited

    Takahiro Moriyama

    THE JOURNAL OF THE INSTITUTE OF ELECTRONICS, INFORMATION AND COMMUNICATION ENGINEERS   Vol. 105 ( 12 ) page: 1400 - 1406   2022.12

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  2. Controlling Antiferromagnetic Order and THz Resonance Invited

    Takahiro Moriyama, Teruo Ono

    Magnetics Japan   Vol. 17 ( 5 ) page: 219 - 226   2022.10

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  3. Magnetization dynamics in Antiferro- and ferri-magnets Invited

    Takahiro Moriyama, Yoichi Shiota, Teruo Ono

      Vol. 77   page: 367 - 372   2022.6

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  4. Quantitative observation of optical activity induced by surface acoustic waves

    久富隆佑, 久富隆佑, 多賀光太郎, 大沼悠一, 佐々木遼, 佐々木遼, 宇佐見康二, 中村泰信, 中村泰信, 塩田陽一, 森山貴広, 小野輝男

    日本物理学会講演概要集(CD-ROM)   Vol. 76 ( 2 )   2021

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  5. スピンホール効果がもたらす驚き(翻訳) Invited

    森山 貴広

    パリティ   Vol. 33   page: 22   2018.5

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  6. 反強磁性体スピントロニクスとデバイスへの展望 Invited

    森山 貴広

    日本磁気学会誌「まぐね」   Vol. 11   page: 143   2016

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  7. Shot noise on pn junction of graphene in the quantum Hall regime

    Matsuo Sadashige, Takeshita Shunpei, Tanaka Takahiro, Nakaharai Shu, Tsukagoshi Kazuhito, Moriyama Takahiro, Ono Teruo, Kobayashi Kensuke

    Meeting Abstracts of the Physical Society of Japan   Vol. 71   page: 1218 - 1218   2016

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    DOI: 10.11316/jpsgaiyo.71.2.0_1218

  8. 強磁性金属多層膜における電流誘起有効磁場のホール測定による決定 Invited

    河口真志, 森山貴広, 小野輝男

    ナノ学会会報   Vol. 13   page: 3   2014.5

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Presentations 144

  1. 反強磁性薄膜のテラヘルツ分光 Invited

    森山貴広

    応用物理学会・日本磁気学会共同主催研究会 「エキゾチック磁性を活用したスピントロニクス研究の最前線」  2024.3.11  応用物理学会、日本磁気学会

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    Event date: 2024.3

    Language:Japanese  

    Venue:東京お茶の水  

  2. Electrical detection of antiferromagnetic dynamics in thin films by using gyrotron Invited

    Takahiro Moriyama

    Symposium on Frontier of Terahertz Science X  2023.12.21 

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    Event date: 2023.12

    Language:English   Presentation type:Oral presentation (invited, special)  

  3. Electrical detection of antiferromagnetic dynamics Invited

    Takahiro Moriyama

    Summit of Materials Science 2023 & GIMRT User Meeting 2023  2023.11.21 

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    Event date: 2023.11

    Language:English   Presentation type:Oral presentation (invited, special)  

  4. Electrical detection of antiferromagnetic dynamics in thin films by using gyrotron

    T. Moriyama, S. Funada, Y. Ishikawa, M. Kimata, Y. Yamaguchi, K. Hayashi, T. Sano, K. Sugi, Y. Fuji, S. Mitsudo, Y. Shiota, T. Ono

    2023.9.28 

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    Event date: 2023.9

    Language:English   Presentation type:Oral presentation (general)  

  5. Spin transport and dynamics in antiferromagnets Invited

    Takahiro Moriyama

    Spin Argentina 2022  2022.11.10 

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    Event date: 2022.11

    Presentation type:Oral presentation (invited, special)  

  6. 反強磁性体を用いたテラヘルツスピントロニクス Invited

    森山貴広

    日本物理学会2022年秋季大会シンポジウム  2022.9.10 

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    Event date: 2022.9

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  7. Spin dynamics and transport in antiferromagnets Invited

    Takahiro Moriyama

    Trends in MAGnetism 2022  2022.9.5 

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    Event date: 2022.9

    Language:English   Presentation type:Oral presentation (invited, special)  

  8. 反強磁性体を用いたテラヘルツスピントロニクス Invited

    森山貴広

    電気学会専門調査委員会  2022.8.26 

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    Event date: 2022.8

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  9. Electrical detection of antiferromagnetic resonance modes by using 154 GHz gyrotron irradiation

    T. Moriyama, S. Funada, K. Hayashi, T. Sano, Y. Ishikawa, Y. Fujii, S. Mitsudo, M. Kimata, Y. Shiota, T. Ono

    the 24th International Colloquium on Magnetic Films and Surfaces (ICMFS-2022)  2022.7.10 

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    Event date: 2022.7

    Language:English   Presentation type:Oral presentation (general)  

  10. 強磁性/反強磁性界面における交換結合とギルバート減衰定数の関係

    池渕徹也, 森山貴広, 水野隼翔, 小田研人, 小野輝男

    日本物理学会講演概要集(CD-ROM)  2018.3.23 

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    Event date: 2018.3

    Language:Japanese  

  11. フェリ磁性体の角運動量補償温度近傍におけるスピントランスファトルク

    奥野尭也, KIM Duck‐Ho, OH Se‐Hyeok, 平田雄翔, 西村幸恵, KIM Se Kwon, 吉川大貴, 二川康宏, 塚本新, 塩田陽一, 森山貴広, KIM Kab‐Jin, LEE Kyung‐Jin, 小野輝男, 小野輝男

    日本物理学会講演概要集(CD-ROM)  2018.3.23 

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    Event date: 2018.3

    Language:Japanese  

  12. イオン液体を用いたCo超薄膜における交換相互作用の電界効果

    石橋未央, 山田貴大, 塩田陽一, 安藤冬希, 小山知弘, 柿堺悠, 水野隼翔, 三輪一元, 小野新平, 森山貴広, 千葉大地, 小野輝男

    日本物理学会講演概要集(CD-ROM)  2018.3.23 

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    Event date: 2018.3

    Language:Japanese  

  13. スピントルク強磁性共鳴法を用いたFeRhに作用するスピントルクの測定

    田中健勝, 森山貴広, 宇佐見喬政, 谷山智康, 小野輝男

    日本物理学会講演概要集(CD-ROM)  2018.3.23 

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    Event date: 2018.3

    Language:Japanese  

  14. スピンホール効果によるCoOの磁化のスピントルク制御

    小田研人, 森山貴広, 森山貴広, 飯野達也, 池渕徹也, 小野輝男, 小野輝男

    日本物理学会講演概要集(CD-ROM)  2018.3.23 

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    Event date: 2018.3

    Language:Japanese  

  15. スピンホール磁気抵抗効果を利用した磁気相転移の検出

    飯野達也, 森山貴広, 森山貴広, 青野晃, 白土優, 小野輝男, 小野輝男

    日本物理学会講演概要集(CD-ROM)  2018.3.23 

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    Event date: 2018.3

    Language:Japanese  

  16. Pt/Co薄膜におけるキュリー温度の電界変調の微視的起源

    安藤冬希, 山田貴大, 小山知弘, 石橋未央, 塩田陽一, 森山貴広, 千葉大地, 小野輝男

    日本物理学会講演概要集(CD-ROM)  2018.3.23 

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    Event date: 2018.3

    Language:Japanese  

  17. Pt/Co/MgO薄膜におけるスピン波伝播の電圧変調

    粕川周平, 塩田陽一, 森山貴広, 小野輝男

    日本物理学会講演概要集(CD-ROM)  2018.3.23 

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    Event date: 2018.3

    Language:Japanese  

  18. フェリ磁性体GdFeCoを用いた磁場駆動磁壁ダイナミクスにおける磁気特性とデピニング磁場の相関

    西村幸恵, KIM Duck‐Ho, 平田雄翔, 奥野尭也, 二川康宏, 吉川大貴, 塚本新, 塩田陽一, 森山貴広, 小野輝男, 小野輝男

    応用物理学会春季学術講演会講演予稿集(CD-ROM)  2018.3.5 

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    Event date: 2018.3

    Language:Japanese  

  19. Pt/Cr<sub>2</sub>O<sub>3</sub>積層膜における非線形ホール効果とX線MCD測定

    白土優, 青野晃, 森山貴広, 鈴木基寛, 中村哲也, 小野輝男, 中谷亮一

    日本金属学会講演概要(CD-ROM)  2018.3.5 

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    Event date: 2018.3

    Language:Japanese  

  20. Temperature dependence of current-induced domain wall velocity in ferrimagnetic GdFeCo/Pt heterostructure

    Okuno T., Kim K.-J., Taniguchi T., Kim S., Hirata Y., Ham W., Yoshikawa H., Tsukamoto A., Moriyama T., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2017  The Physical Society of Japan

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    Event date: 2017

    Language:Japanese  

  21. Measurement of the attempt frequency in the domain wall motion using rf current

    Taniguchi T., Kim K.-J., Moriyama T., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2017  The Physical Society of Japan

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    Event date: 2017

    Language:Japanese  

  22. Domain wall resistance in ferrimagnetic GdFeCo

    Hirata Y., Kim K.-J., Taniguchi T., Kim S., Okuno T., Ham W.S., Yoshikawa H., Tsukamoto A., Moriyama T., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2017  The Physical Society of Japan

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    Event date: 2017

    Language:Japanese  

  23. 19aAU-8 Soliton-like magnetic domain wall motion induced by the interfacial Dzyaloshinskii-Moriya interaction

    Yoshimura Yoko, Kim Kab-Jin, Taniguchi Takuya, Tono Takayuki, Ueda Kohei, Hiramatsu Ryo, Moriyama Takahiro, Yamada Keisuke, Nakatani Yoshinobu, Ono Teruo

    Meeting Abstracts of the Physical Society of Japan  2016  The Physical Society of Japan (JPS)

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    Event date: 2016

    Language:Japanese  

  24. Shot noise on pn junction of graphene in the quantum Hall regime

    Matsuo Sadashige, Takeshita Shunpei, Tanaka Takahiro, Nakaharai Shu, Tsukagoshi Kazuhito, Moriyama Takahiro, Ono Teruo, Kobayashi Kensuke

    Meeting Abstracts of the Physical Society of Japan  2016  The Physical Society of Japan

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    Event date: 2016

    Language:Japanese  

  25. Electric field effect on exchange stiffness in MgO/Co/Pt system

    Ando F., Kakizakai H., Koyama T., Yamada K., Kawaguchi M., Kim S., Kim K-J., Moriyama T., Chiba D., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2016  The Physical Society of Japan

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    Event date: 2016

    Language:Japanese  

  26. 21pBC-10 Temperature dependence of spin Hall magnetoresistance effect

    Okuno T., Taniguchi T., Kim S., Moriyama T., Baek S. C., Park B.-G., Kim K.-J., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2016  The Physical Society of Japan (JPS)

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    Event date: 2016

    Language:Japanese  

  27. 19pPSB-55 Characterization of the anisotropic g-factor in sub-nanometer Fe film by ferromagnetic resonance

    Mizuno H., Moriyama T., Kawaguchi M., Tanaka K., Koyama T., Chiba D., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2016  The Physical Society of Japan (JPS)

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    Event date: 2016

    Language:Japanese  

  28. 19pPSB-50 Electric field modulation of current induced effective fields in ferromagnetic multiple layers

    Kawaguchi M., Moriyama T., Mizuno H., Yamada K., Kakizakai H., Koyama T., Ono S., Miwa K., Chiba D., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2016  The Physical Society of Japan (JPS)

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    Event date: 2016

    Language:Japanese  

  29. 19pPSB-49 Exchange bias Dependence of damping constant on relative angle between magnetization and exchange bias

    Kamiya M., Moriyama T., Oda K., Tanaka K., Kawaguchi M., Kim Kab-Jin, Ono T.

    Meeting Abstracts of the Physical Society of Japan  2016  The Physical Society of Japan (JPS)

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    Event date: 2016

    Language:Japanese  

  30. 19pPSB-48 Temperature dependence of field-driven magnetic domain wall velocity in ferrimagnetic GdFeCo wires

    Tono T., Kim Kab-Jin, Okuno T., Moriyama T., Tsukamoto A., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2016  The Physical Society of Japan (JPS)

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    Event date: 2016

    Language:Japanese  

  31. 19pPSB-47 Domain control by electric current in antiferromagnetic FeRh nanowires

    Matsuzaki N., Moriyama T., Kim Kab-Jin, Suzuki I., Taniyama T., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2016  The Physical Society of Japan (JPS)

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    Event date: 2016

    Language:Japanese  

  32. 19pPSB-46 Electric field induced domain wall motion in MgO/Co/Pt system

    Kakizakai H., Ando F., Yamada K., Kawaguchi M., Moriyama T., Kim Kab-Jin, Koyama T., Chiba D., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2016  The Physical Society of Japan (JPS)

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    Event date: 2016

    Language:Japanese  

  33. 19pPSB-45 Deformation of domain structure induced by electric field

    Ando F., Kakizakai H., Yamada K., Kawaguchi M., Koyama T., Chiba D., Kim Kab-Jin, Moriyama T., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2016  The Physical Society of Japan (JPS)

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    Event date: 2016

    Language:Japanese  

  34. 19pPSB-35 Spin Hall effect in ferromagnets measured by spin-torque FMR

    Tanaka K., Moriyama T., Kamiya M., Mizuno H., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2016  The Physical Society of Japan (JPS)

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    Event date: 2016

    Language:Japanese  

  35. 19pPSB-23 Electric modulation of induced magnetic moment in Pt layer

    Yamada K., Koyama T., Kim Sanghoon, Kawaguchi M., Ando F., M. Hayato, Kim Kab-Jin, Kakizakai H., Moriyama T., M. Kazumoto, Ono S., Suzuki M., Chiba D., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2016  The Physical Society of Japan (JPS)

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    Event date: 2016

    Language:Japanese  

  36. 19pPSB-22 Electric current control of exchange bias in metallic antiferromagnets

    Oda K., Moriyama T., Kamiya M., Tanaka K., Kawaguchi M., Kim Kab-Jin, Ono T.

    Meeting Abstracts of the Physical Society of Japan  2016  The Physical Society of Japan (JPS)

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    Event date: 2016

    Language:Japanese  

  37. 19aAU-9 Correlation between orbital magnetism and the Dzyaloshinkii-Moriya interaction

    Kim Sanghoon, Ueda Kohei, Yamada Kihiro, Suzuki Motohiro, Kotani Yoshinori, Nakamura Tetsuya, Nakamura Kohji, Koyama Tomohiro, Chiba Daichi, Moriyama Takahiro, Kim Kab-Jin, Ono Teruo

    Meeting Abstracts of the Physical Society of Japan  2016  The Physical Society of Japan (JPS)

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    Event date: 2016

    Language:English  

  38. Temperature dependence of magnetoresistances in ferrimagnetic GdFeCo/Pt heterostructure

    Okuno T., Kim K.-J., Tono T., Kim S., Yoshikawa H., Tsukamoto A., Moriyama T., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2016  The Physical Society of Japan

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    Event date: 2016

    Language:Japanese  

  39. Detection of magnetoresistance in metallic antiferromagnets

    Oda K., Moriyama T., Kamiya M., Kim K.-J., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2016  The Physical Society of Japan

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    Event date: 2016

    Language:Japanese  

  40. 18pCM-1 Domain wall manipulation by nanosecond pulse current

    Taniguchi T., Kim K.-J., Tono T., Moriyama T., Nakatani Y., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2015  The Physical Society of Japan (JPS)

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    Event date: 2015

    Language:Japanese  

  41. 23pAD-9 Nernst effect influence on the determination of current induced effective field in ferromagnetic multiple layers

    Kawaguchi M., Moriyama T., Koyama T., Chiba D., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2015  The Physical Society of Japan (JPS)

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    Event date: 2015

    Language:Japanese  

  42. 23pAD-4 Field-driven domain wall motion in GdFeCo wires with perpendicular magnetic anisotropy

    Tono T., Taniguchi T., Kim Kab-Jin, Moriyama T., Tsukamoto A., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2015  The Physical Society of Japan (JPS)

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    Event date: 2015

    Language:Japanese  

  43. 23pAD-2 Wire-width dependence of current-driven domain-wall creep motion

    Taniguchi T., Tono T., Kim Kab-Jin, Moriyama T., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2015  The Physical Society of Japan (JPS)

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    Event date: 2015

    Language:Japanese  

  44. 23pAD-1 Magnetic domain-wall oscillator controlled by magnetic field and dc current

    Hiramatsu R., Kim Kab-Jin, Taniguchi T., Tono T., Moriyama T., Fukami S., Yamanouchi M., Ohno H., Nakatani Y., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2015  The Physical Society of Japan (JPS)

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    Event date: 2015

    Language:Japanese  

  45. 21pPSA-34 Spin wave refraction at the interface between films with different thicknesses

    Hata H., Moriyama T., Tanabe K., Kobayashi K., Matumoto R., Murakami S., Ohe J., Chiba D., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2015  The Physical Society of Japan (JPS)

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    Event date: 2015

    Language:Japanese  

  46. 21pPSA-32 Magnetic properties in epitaxial NiO/Pt films

    Matsuzaki N., Moriyama T., Nagata M., Yoshimura Y., Terashima T., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2015  The Physical Society of Japan (JPS)

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    Event date: 2015

    Language:Japanese  

  47. 21pPSA-31 Time-of-flight measurements of current-induced domain wall motion

    Yoshimura Yoko, Taniguchi Takuya, Tono Takayuki, Kim Kab-Jin, Moriyama Takahiro, Ono Teruo

    Meeting Abstracts of the Physical Society of Japan  2015  The Physical Society of Japan (JPS)

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    Event date: 2015

    Language:Japanese  

  48. 21pPSA-27 Spin pumping and magnetic dynamics of synthetic antiferromagnets

    Nagata M., Moriyama T., Kamiya M., Tanaka K., Seki T., Takanashi K., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2015  The Physical Society of Japan (JPS)

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    Event date: 2015

    Language:Japanese  

  49. 21aPS-66 Layer thickness dependence of the g-factor in Pt/Fe multilayers

    Mizuno H., Moriyama T., Kawaguchi M., Nagata M., Tanaka K., Koyama T., Chiba D., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2015  The Physical Society of Japan (JPS)

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    Event date: 2015

    Language:Japanese  

  50. 21aAD-2 Spin current in synthetic antiferromagnet II

    Tanaka K., Moriyama T., Nagata M., Mizuno H., Seki T., Takanashi K., Chiba T., Takahashi S., Bauer Gerrit E. W., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2015  The Physical Society of Japan (JPS)

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    Event date: 2015

    Language:Japanese  

  51. 21aAD-11 Observation of thermal gradient induced by magnon Hall effect

    Tanabe K., Matsumoto R., Ohe J., Murakami S., Moriyama T., Chiba D., Kobayashi K., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2015  The Physical Society of Japan (JPS)

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    Event date: 2015

    Language:Japanese  

  52. 21aAC-10 1/f noise measurement in graphene p-n junction

    Takeshita S., Matsuo S., Tanaka T., Nakaharai S., Tsukagoshi K., Moriyama T., Ono T., Kobayashi K.

    Meeting Abstracts of the Physical Society of Japan  2015  The Physical Society of Japan (JPS)

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    Event date: 2015

    Language:Japanese  

  53. 18pCM-8 Spin current in synthetic antiferromagnet III

    Tanaka K., Moriyama T., Nagata M., Mizuno H., Seki T., Takanashi K., Chiba T., Takahashi S., Bauer Gerrit E. W., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2015  The Physical Society of Japan (JPS)

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    Event date: 2015

    Language:Japanese  

  54. 18pCM-2 Electric field dependence of the g-factor in Pt/Fe ultrathin films

    Mizuno H., Moriyama T., Kawaguchi M., Tanaka K., Koyama T., Chiba D., Ono T.

    Meeting Abstracts of the Physical Society of Japan  2015  The Physical Society of Japan (JPS)

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    Event date: 2015

    Language:Japanese  

  55. 27aXA-11 Spin injection into an antiferromagnetic FeMn alloy

    Moriyama T, Nagata M, Ueda K, Kim Kab-Jin, Chiba D, Ono T

    Meeting Abstracts of the Physical Society of Japan  2013  The Physical Society of Japan

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    Event date: 2013

    Language:Japanese  

  56. Preparation and magnetore sistance in single-crystal and polycrystal Fe/MgO/FeCo tunnel junctions

    Moriyama T., Mitani S., Takanashi K.

    Meeting abstracts of the Physical Society of Japan  2003.3.6  The Physical Society of Japan (JPS)

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    Event date: 2003.3

    Language:Japanese  

  57. Preparation and magnetoresistance of single crystal Fe/CaF_2/CoFe junctions

    MORIYAMA T., MITANI S., TAKANASHI K.

    2002.9.1 

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    Event date: 2002.9

    Language:Japanese  

  58. Spin dependent transport in Fe/CaF_2/Fe junctions

    Moriyama T., Mitani S., Takanashi K.

    Meeting abstracts of the Physical Society of Japan  2002.8.13  The Physical Society of Japan (JPS)

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    Event date: 2002.8

    Language:Japanese  

  59. 25pXJ-4 Preparation and magnetoresistance of ferromagnetic tunnel junctions with MgF_2 and MgO insulating barriers

    Moriyama T., Mitani S., Takanashi K.

    Meeting abstracts of the Physical Society of Japan  2002.3.1  The Physical Society of Japan (JPS)

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    Event date: 2002.3

    Language:Japanese  

  60. 強磁場を用いた反強磁性磁化ダイナミクスの測定 Invited

    森山貴広

    強磁場オンライン研究会  2021.11.30 

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    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  61. 反強磁性体NiOを介したスピントランスファー

    森山貴広, So Takei, 永田真己, 吉村瑶子, 松崎乃里子, 寺嶋孝仁, Yaroslav Tserkovnyak, 小野輝男

    応用物理学会秋季講演会  2015.9.14 

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    Venue:名古屋、愛知  

  62. 反強磁性体における スピン変換ダイナミクスの解明 Invited

    森山貴広

    2017年度第1回スピントロニクス研究会  2017.4.14 

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    Venue:御茶ノ水、東京  

  63. Spintronic operations with antiferromagnets Invited

    Takahiro Moriyama

    ATI spintronics meeting  2019.8.22 

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  64. Antiferromagnetic spintronics Invited

    Takahiro Moriyama

    JSAP Fall meeting  2019.9.19 

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    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  65. Toward antiferromagnetic THz spintronics Invited

    The Physical Society of Japan 2021 annual meeting, symposium  2021.3.12 

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    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  66. 反強磁性体磁化ダイナミクスのTHzスペクトロスコピー Invited

    森山貴広

    日本磁気学会 第229回研究会 「テラヘルツ領域におけるスピントロニクス研究の現状と展望」  2020.11.11 

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    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  67. CONTROLLING ANTIFERROMAGNETIC RESONANCES Invited

    Takahiro Moriyama

    The 44th annual conference in magnetics in Japan  2020.12.14 

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  68. 反強磁性磁化のスピントルク制御 Invited

    森山貴広

    第65回日本磁気学会スピンエレクトロニクス専門会  2017.11.22 

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    Venue:中央大学、東京  

  69. How antiferromagnetic domains evolve: experiments and simulations (https://www.youtube.com/watch?v=qvaYS43OeQs) Invited

    Takahiro Moriyama

    Virtual workshop of PETASPIN  2021.2.26 

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  70. 反強磁性体FeMn合金へのスピン注入に関する研究

    森山貴広, 永田真己, Kab-Jin Kim, 小野輝男

    日本物理学会春季大会  2013.3.27 

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    Venue:広島大学、広島  

  71. Spin and Charge Pumping in Magnetic Tunneling Structures Invited International conference

    T. Moriyama, J. Q. Xiao

    ICMAT conference  2009.7.2 

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    Venue:Singapore  

  72. Spin dissipation depending on magnetic moment orientation in antiferromagnets Invited International conference

    T. Moriyama

    York-Tohoku-Kaiserslautern Symposium  2017.6.22 

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    Venue:York; UK  

  73. Spin dissipation depending on magnetic moment orientation in antiferromagnets Invited International conference

    T. Moriyama, M. Kamiya, K. Oda, K. Tanaka, K.-J. Kim, T. Ono

    Korea-Japan Spin-Orbit Workshop  2016.12.15 

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    Language:English   Presentation type:Oral presentation (invited, special)  

    Venue:Kyusyu University; Fukuoka  

  74. Spin dynamics and transport in antiferromagnets Invited

    Takahiro Moriyama

    IJW-IPS 2022 Indo-Japan workshop  2022.3.9 

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    Language:English   Presentation type:Oral presentation (invited, special)  

  75. Spin orbit torque in antiferromagnets Invited International conference

    T. Moriyama

    Yound research leaders group workshope - insulator spintronics-  2017.8.3 

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    Venue:Mainz; Germany  

  76. Spin torque control of antiferromagnetic moments in NiO Invited International conference

    T. Moriyama

    International Conference on Magnetism  2018.7.20 

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    Language:English   Presentation type:Oral presentation (invited, special)  

    Venue:San Francisco; USA  

  77. Spin torque control of antiferromagnetic NiO Invited International conference

    Takahiro Moriyama

    16th RIEC International Workshop on Spintronics  2019.1 

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  78. Spin Torque Effects in Spin Valves and Magnetic Tunnel Junctions Invited International conference

    T. Moriyama, D. C. Ralph

    2nd Spintronics and Spin caloritronics Workshop  2010.2.8 

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    Language:English   Presentation type:Oral presentation (invited, special)  

    Venue:Sendai; Japan  

  79. Spin torque ferromagnetic resonance measurements in antiferromagnetic multilayers Invited International conference

    T. Moriyama

    NIST Electron physics group seminar  2014.9.30 

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    Venue:Gaithersburg; MA; USA  

  80. Spin torque ferromagnetic resonance measurements in antiferromagnetic multilayers Invited International conference

    T. Moriyama

    Condensed matter physics seminar at University of Delaware  2014.11.17 

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    Language:English   Presentation type:Oral presentation (invited, special)  

    Venue:Newark; DE; USA  

  81. Spin torque ferromagnetic resonance measurements in antiferromagnetic multilayers International conference

    T. Moriyama, M. Nagata, K. Tanaka, K.-J. Kim, H. Almasi, W. G. Wang, T. Ono

    KAUST Spin-Orbit Torque Workshop  2015.2.28 

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    Language:English   Presentation type:Oral presentation (general)  

    Venue:KAUST; Thuwal; Saudi Arabia  

  82. Spin torque ferromagnetic resonance measurements in antiferromagnetic multilayers Invited International conference

    T. Moriyama

    New Perspectives in Spintronic and Mesoscopic Physics (NPSMP2015)  2015.6.10 

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    Venue:Kashiwa; Chiba; Japan  

  83. Spin torque ferromagnetic resonance measurements on FeCoB/IrMn/Pt multilayers International conference

    T. Moriyama, M. Nagata, K. Tanaka, K.-J. Kim, H. Almasi, W. G. Wang, T. Ono

    Magnetism and Magnetic Materials Conference  2014.11.5 

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    Language:English   Presentation type:Oral presentation (general)  

    Venue:Honolulu; HI; USA  

  84. Spin torque in antiferromagnets Invited International conference

    T. Moriyama

    ETH-Kyoto Miniworkshop  2017.10.20 

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    Venue:Kyoto; Japan  

  85. Spin torque switching and magnetoresistive detection in antiferromagnets Invited International conference

    T. Moriyama

    19th International Symposium on the Physics of Semiconductors and Applications  2018.7.3 

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    Venue:Jeju; Korea  

  86. Spin torque switching of antiferromagnets Invited International conference

    T. Moriyama

    2nd IEEE Conference on Advances in Magnetics  2018.2.8 

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    Venue:La Thuile; Italy  

  87. Spin transfer in antiferromagnet Invited International conference

    T. Moriyama

    SPIE Optics photonics Nanoscience engineering  2016.8.28 

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    Venue:San Diego; CA; USA  

  88. Spin transfer torque in antiferromagnet and toward the applications Invited International conference

    T. Moriyama

    International conference on solid state devices and materials  2016.9.27 

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    Venue:Tsukuba; Ibaraki  

  89. Spin transfer torque in magnetic tunnel junctions with a perpendicularly magnetized polarizer International conference

    T. Moriyama, T. J. Gudmundsen, L. Liu, R. A. Buhrman, D. C. Ralph

    APS March Meeting  2011.3.24 

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    Venue:Dallas; TX; USA  

  90. Spintronic operations with antiferromagnets Invited International conference

    Takahiro Moriyama

    Magnonics 2019  2019.7.29 

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  91. Spintronic operations with antiferromagnets Invited International conference

    Takahiro Moriyama

    SPICE-Workshop Antiferromagnetic Spintronics -  2019.10.8 

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  92. Spintronic operations with antiferromagnets Invited International conference

    Takahiro Moriyama

    International workshop Spintronics 2019 - Spin Peru-  2019.10.22 

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  93. Spintronic operations with antiferromagnets Invited International conference

    Takahiro Moriyama

    Material Research Meeting 2019  2019.12.11 

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  94. Tunnel barrier enhanced voltage signals generated by magnetization precession of a single ferromagnetic layer Invited International conference

    T. Moriyama, J. Q. Xiao

    Magnetism and Magnetic Materials Conference  2008.11.12 

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    Venue:Austin; TX; USA  

  95. Tunnel barrier enhanced voltage signals generated by magnetization precession of a single ferromagnetic layer Invited International conference

    T. Moriyama

    APS March Meeting  2009.3.17 

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    Venue:Pittsburgh; PA; USA  

  96. Tunnel barrier enhanced voltage signals generated by magnetization precession of a single ferromagnetic layer Invited International conference

    T. Moriyama, J. Q. Xiao

    INTERMAG  2009.5.5 

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    Venue:Sacramento; CA; USA  

  97. Tunnel Magnetoresistance and Spin Torque Switching in MgO-based Magnetic Tunnel Junctions with a Co/Ni Multilayer Electrode International conference

    T. Moriyama, T. J. Gudmundsen, P. Y. Huang, L. Liu, D. A. Muller, R. A. Buhrman, D. C. Ralph

    APS March Meeting  2010.3.16 

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    Venue:Portland; OR; USA  

  98. Tunnel Magnetoresistance and Spin Torque Switching in MgO-based Magnetic Tunnel Junctions with a Co/Ni Multilayer Electrode Invited International conference

    T. Moriyama

    IBM T. J. Watson Research Center MRAM Seminer  2010.5.21 

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    Venue:Yorktown Heights; NY; USA  

  99. Tunnel Magnetoresistance and Spin Torque Switching in MgO-based Magnetic Tunnel Junctions with a Co/Ni Multilayer Electrode International conference

    T. Moriyama, T. J. Gudmundsen, P. Y. Huang, L. Liu, D. A. Muller, R. A. Buhrman, D. C. Ralph

    Magnetism and Magnetic Materials Conference  2010.11.17 

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    Language:English   Presentation type:Oral presentation (general)  

    Venue:Atlanta; GA; USA  

  100. Tunnel Magnetoresistance and Spin Torque Switching in MgO-based Magnetic Tunnel Junctions with a Co/Ni Multilayer Electrode Invited International conference

    T. Moriyama, T. J. Gudmundsen, L. Liu, R. A. Buhrman, D. C. Ralph

    Magnetism and Magnetic Materials Conference  2011.11.1 

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    Venue:Scottsdale; AZ; USA  

  101. Tunneling magnetoresistance in FeCo/MgO/FeCo tunneling junctions depending on FeCo/MgO interface state International conference

    T. Moriyama, W. G. Wang, J. Q. Xiao

    INTERMAG  2006.5.9 

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    Venue:San Diego; CA; USA  

  102. Tunneling magnetoresistance in MgO-based magnetic tunneling junction with (001) oriented FeCo electrode fabricated by sputtering deposition International conference

    T. Moriyama, W. G. Wang, J. Q. Xiao

    APS March Meeting  2006.3.16 

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    Venue:Baltimore; MD; USA  

  103. スピントルク強磁性共鳴を用いた反強磁性体へのスピン注入の研究 Invited

    森山貴広

    第52回日本磁気学会スピンエレクトロニクス専門会  2015.1.28 

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    Venue:金属材料研究所、仙台  

  104. スピントロニクスの最前線 Invited

    森山貴広

    電子情報通信学会 2022年総合大会  2022.3.17 

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    Language:Japanese   Presentation type:Public lecture, seminar, tutorial, course, or other speech  

  105. テラヘルツ帯の反強磁性共鳴によるスピンポンピング効果 Invited

    森山貴広

    応用電子物性分科会 11月研究例会  2021.11.12 

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    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  106. フッ化物絶縁層を用いた強磁性トンネル接合の作製と磁気抵抗効果

    森山貴広, 三谷誠司, 高梨弘毅

    日本金属学会春季講演会  2002.3.30 

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    Venue:東京理科大学、東京  

  107. 単結晶Fe/CaF2/CoFe接合の作製と磁気抵抗効果

    森山貴広, 三谷誠司, 高梨弘毅

    第26回 日本応用磁気学会学術講演会  2002.9.17 

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    Venue:東京農工大、東京  

  108. 反強磁性スピントロニクス Invited

    森山貴広

    京都大学化学研究所第111回研究発表会  2017.12.1 

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    Venue:京都大学、宇治  

  109. 反強磁性スピントロニクスとデバイスへの展望 Invited

    森山貴広

    大阪大学 産業科学研究所ナノテクセンター若手セミナー  2017.3.6 

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    Venue:梅田、大阪  

  110. 反強磁性スピントロニクスとデバイスへの展開 Invited

    森山貴広

    日本磁気学会第209回研究会  2016.10.21 

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    Language:English   Presentation type:Oral presentation (invited, special)  

    Venue:中央大学、東京  

  111. 反強磁性体FeMn合金へのスピン注入

    森山貴広, 永田真己, Kab-Jin Kim, 小野輝男

    応用物理学会秋季講演会  2013.9.20 

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    Venue:立命館大学、京都  

  112. Preparation and TMR of MgF2-based magnetic tunnel junctions International conference

    T. Moriyama, S. Mitani, K. Takanashi

    International Colloquium on Magnetic Films and Surfaces  2002.3.15 

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    Venue:Kyoto; Japan  

  113. Anti-damping spin transfer torque through antiferromagnet Invited International conference

    T. Moriyama

    32nd Reimei Workshop on Frontiers of Condensed Matter Physics  2015.11.17 

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    Venue:Tohoku U.; Sendai; Japan  

  114. Anti-damping spin transfer torque through epitaxial Nickel oxide International conference

    T. Moriyama, S. Takei, M. Nagata, Y. Yoshimura, N. Matsuzaki, T. Terashima, Y. Tserkovnyak, T. Ono

    Joint MMM/Intermag Conference  2016.1.12 

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    Venue:San Diego; CA; USA  

  115. Antiferromagnetic spintronics Invited

    Takahiro Moriyama

    Physics department synposium at Denver University  2019.10.30 

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  116. Antiferromagnetic spintronics Invited

    Takahiro Moriyama

    Physics department synposium at University of Arizona  2019.11.1 

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  117. Antiferromagnetic spintronics and our recent results Invited International conference

    T. Moriyama

    University of Messina Seminar  2018.1.25 

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    Venue:Messina; Italy  

  118. Antiferromagnetic spintronics and recent results Invited International conference

    T. Moriyama

    Special seminar in Institute for Materials Research; Tohoku University  2016.5.23 

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    Venue:Sendai; Japan  

  119. Antiferromagnetic spintronics and recent results Invited International conference

    T. Moriyama

    International workshop on Nano-Spin Conversion Science and Quantum Spin Dynamics  2016.10.12 

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    Venue:Univ. of Tokyo; Tokyo  

  120. Choking nonlocal magnetic damping in exchange-biased ferromagnets International conference

    Takahiro Moriyama, K. Oda, T. Ono

    Magnetism and Magnetic Materials Conference  2019.11.5 

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  121. Co/フッ化物積層膜の構造とスピン依存伝導

    森山貴広, 三谷誠司, 高梨弘毅

    第25回 日本応用磁気学会学術講演会  2001.9.28 

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    Venue:秋田大学、秋田  

  122. Controlling antiferromagnetric resonance Invited

    Takahiro Moriyama

    Intermag 2021  2021.4.29 

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  123. Controlling antiferromagnetric resonance Invited

    Takahiro Moriyama

    Online spintronics seminar  2021.5.19 

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  124. Controlling magnetic damping with antiferromagnets Invited International conference

    Takahiro Moriyama

    The 6th Italian Conference on Magnetism  2019.1.31 

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  125. Effect of work function in Co/Al-O/CoGd magnetic tunnel junctions International conference

    T. Moriyama, W. G. Wang, J. Q. Xiao

    Joint MMM/Intermag Conference  2007.1.8 

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    Venue:Baltimore ;MD; USA  

  126. Electric field controlled orbital moment: A correlation to magnetic anisotropy modulation International conference

    T. Moriyama, H. Mizuno, K. Tanaka, M. Kawaguchi, T. Koyama, D, Chiba, T. Ono

    Magnetism and Magnetic Materials Conference  2017.11.9 

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    Venue:Pittsburgh; PA; USA  

  127. Exchange bias dependence of damping parameter in antiferromagnetic multilayer

    K. Oda

    応用物理学会秋季講演会  2016.9.16 

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    Venue:新潟市、新潟  

  128. FePt規則合金を用いたトンネル接合の作製と磁気抵抗効果

    森山貴広, 三谷誠司, 関 剛斎, 嶋 敏之, 塚本和彦, 高梨弘毅

    応用物理学会春期講演会  2003.3.20 

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    Venue:神奈川大学、横浜  

  129. Ferromagnetic resonance linewidth in FeCo/NM/Py (NM=Pt; Cu) spin valves International conference

    T. Moriyama, X. Fan, R. Cao, B. Nikolic, Q. Wen, H. W. Zhang, J. Q. Xiao

    Magnetism and Magnetic Materials Conference  2007.11.6 

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    Venue:Tampa; FL; USA  

  130. FMR spectroscopy with very large precession cone angle in magnetic tunnel junctions International conference

    T. Moriyama, X. Fan, J. Q. Xiao

    APS March Meeting  2008.3.14 

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    Venue:New Orleans; LA; USA  

  131. Magnetization control and detection of antiferromagnetic NiO Invited International conference

    Takahiro Moriyama

    Joint MMM/Intermag Conference  2019.1.16 

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  132. Magnetization dynamics under a strong spin-orbit torque in W/FeCoB/MgO layers International conference

    T. Moriyama, K.-J. Kim, S.-H. C. Baek, B.-G. Park, S-.W. Lee, K.-J. Lee, T. Ono

    Magnetism and Magnetic Materials Conference  2016.11.4 

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    Venue:New Orleans; LA; USA  

  133. Microwave assist magnetization reversal in Ni80Fe20/AlOx/Fe30Co70 magnetic tunnel junctions International conference

    T. Moriyama, R. Cao, J. Q. Xiao, J. Lu, X. Wang, Q. Wen, H. W. Zhang

    Magnetism and Magnetic Materials Conference  2007.11.8 

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    Venue:Tampa; FL; USA  

  134. Microwave assisted magnetization reversal International conference

    T. Moriyama, R. Cao, J. Q. Xiao, L. Jie, W. Xiangrong

    The 5th International Workshop on High Frequency Micromagnetic Devices and Materials  2007.1.13 

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    Venue:The Johns Hopkins University; Baltimore; MD; USA  

  135. Microwave-Assisted Magnetization Switching of Ni80Fe20 in Magnetic Tunnel Junctions International conference

    T. Moriyama, R. Cao, J. Lu, X. Wang, J. Q. Xiao

    MORIS Workshop on Thermal and Optical Magnetic Materials and Devices  2007.9.25 

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    Venue:Carnegie Mellon University; Pittsburgh; PA; USA  

  136. Narrow linewidths for a spin transfer torque oscillator with two perpendicularly-oriented polarizer layers and two coupled in-plane-oriented free layers International conference

    T. Moriyama, R. A. Buhrman, D. C. Ralph

    Magnetism and Magnetic Materials Conference  2010.1.18 

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    Venue:Washington; DC; USA  

  137. Negative TMR in Magnetic Tunneling Junctions with Zr oxide barrier International conference

    T. Moriyama, W. G. Wang, Xiaohai Xiang, J. Q. Xiao

    APS March Meeting  2005.3.21 

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    Venue:Los Angels. CA; USA  

  138. Nonlocal and local magnetization dynamics excited by a rf magnetic field in magnetic multilayers Invited International conference

    T. Moriyama

    New York University Seminar  2008.4.2 

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    Venue:New York; NY; USA  

  139. Nonlocal and local magnetization dynamics excited by a rf magnetic field in magnetic multilayers Invited International conference

    T. Moriyama

    Carnegie Mellon University Seminar  2008.4.10 

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    Venue:Pittsburgh; PA; USA  

  140. Nonlocal and local magnetization dynamics excited by a rf magnetic field in magnetic multilayers Invited International conference

    T. Moriyama

    Seagate Research Center Seminar  2008.4.11 

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    Venue:Pittsburgh; PA; USA  

  141. Nonlocal and local magnetization dynamics excited by a rf magnetic field in magnetic multilayers Invited International conference

    T. Moriyama

    National Institute of Standards and Technology Seminar  2008.5.2 

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    Venue:Gaithersburg; MA; USA  

  142. Nonlocal and local magnetization dynamics excited by a rf magnetic field in magnetic multilayers Invited International conference

    T. Moriyama

    Cornell University Seminar  2008.5.5 

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    Venue:Ithaca; NY; USA  

  143. 反強磁性体を用いたスピントロニクスの開拓 Invited

    森山貴広

    文科省と附置研センターとの定例ランチミーティング第25回  2022.12.2 

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    Presentation type:Symposium, workshop panel (nominated)  

  144. 反強磁性薄膜のTHz分光 Invited

    森山貴広

    第2回 強磁場コラボラトリー オンラインセミナー  2023.7.7 

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    Presentation type:Oral presentation (invited, special)  

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KAKENHI (Grants-in-Aid for Scientific Research) 9

  1. Generation and detection of non-trivial spin current in synthetic altermagnets

    Grant number:23KK0093  2023.9 - 2027.3

    Grants-in-Aid for Scientific Research  Fund for the Promotion of Joint International Research (International Collaborative Research)

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    Authorship:Principal investigator 

    Grant amount:\19760000 ( Direct Cost: \15200000 、 Indirect Cost:\4560000 )

  2. 反強磁性体テラヘルツスピントロニクスの創成

    Grant number:21H04562  2021.4 - 2024.3

    日本学術振興会  科学研究費助成事業  基盤研究(A)

    森山 貴広, 中村 浩次, 中村 浩次

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    Authorship:Principal investigator 

    Grant amount:\43160000 ( Direct Cost: \33200000 、 Indirect Cost:\9960000 )

    これまでスピントロニクスにおける主材料は専ら強磁性体であり、反強磁性体は様々な固定概念から応用・基礎研究がほとんど行われてこなかった材料・物理系であった。しかしながら、近年、申請者自身の主導するものを含む研究成果から、伝導電子スピンと反強磁性体の局在磁気モーメント(局在スピン)との相互作用が存在することが実験的に明らかになってきた。これらの成果を糸口として、「反強磁性体スピントロニクス」の研究が活発化している。本研究では、これらの研究成果をさらに発展させ、反強磁性体が持つ超高周波(THz帯域)の磁気共鳴周波数を積極的に利用した「反強磁性体テラヘルツスピントロニクス」の学理を構築し、スピントロニクスの動作原理を利用した次世代テラヘルツ基盤技術を創成することを目的とする。
    本年度は、α-Fe2O3の反強磁性共鳴について調査した。α-Fe2O3のFe3+カチオンをAl、Ru、Rh、Inなどで置換しことで反強磁性共鳴周波数を0.2~1THzの範囲で制御することに成功している。また、モーリン温度(α-Fe2O3の磁気異方性がゼロになる温度)と共鳴周波数の相関から、α-Fe2O3の磁気異方性の増減や共鳴周波数の変化についてミクロスコピックなメカニズムを考察し、解明した。これらの結果は、α-Fe2O3がポスト5Gなどの通信周波数>30GHzにおいて、フィルターや吸収材として利用可能な材料であることを示した重要な成果である。

  3. Exploration of ultra-high speed spintronic devices using antiferromagnets

    Grant number:19K21972  2019.6 - 2021.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Challenging Research (Exploratory)

    Takahiro Moriyama

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    Authorship:Principal investigator 

    Grant amount:\6500000 ( Direct Cost: \5000000 、 Indirect Cost:\1500000 )

    The purpose of this study is to understand the antiferromagnetic magnetization dynamics in the ultra-short time domain and to demonstrate the magnetization reversal device. First, we investigated the magnetization dynamics of antiferromagnetic materials such as NiO and α-Fe2O3, and found that the resonance frequency and damping constant, which are important for understanding the magnetization dynamics, can be controlled depending on the crystallinity and cation substitution elements. Second, we devised a photoconductive switch which generates and injects a picosecond current pulse into the antiferromagnetic element to reverse the magnetization. The magnetization reversal has not been clearly captured yet. Meanwhile, some issues have been identified regarding the optimization of the photoconductive switch and the current pulse introduction method. The research will be continued to achieve the goals.

  4. Spin dynamics in antiferromagnetic nanofilms studied by phonon-magnon interaction

    Grant number:18H01859  2018.4 - 2022.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

    Nagakubo Akira

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    Authorship:Coinvestigator(s) 

    In this study, we studied the fundamental phono properties of NiO and the interaction between magnon and GHz-range longitudinal phonon to reveal and apply the phonon-magnon coupling in antiferromagnets. Our measurement for Pt/NiO/Pt nanofilms revealed that the elastic constant of NiO largely changes depending on deposition conditions and substrates. From ultrasound resonance spectroscopy measurement for a single bulk crystal, we also found that the antiferromagnetic order seriously affects the phonon properties, which change with deformation modes. These results will contribute to further study and application of the phonon properties of antiferromagnetic films.

  5. spin torque operation for antiferromagnetic spin devices

    Grant number:17H04924  2017.4 - 2020.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Young Scientists (A)

    Moriyama Takahiro

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    Authorship:Principal investigator 

    Grant amount:\24180000 ( Direct Cost: \18600000 、 Indirect Cost:\5580000 )

    Antiferromagnets have multiple magnetic sublattices and the magnetic moments on the sublattices are compensated by each other. Negligible net magnetization and small magnetic susceptibility of antiferromagnets were considered useless in spintronics. However, the present research found the possibility of the spin torque manipulation of the antiferromagnetic magnetic moment and the electrical reading of the direction of the magnetic moment. Based on the findings, non-volatile spin-torque operated antiferromagnetic memory devices were demonstrated. The achievement of this research strongly suggests that antiferromagnets can be novel and useful materials in spintronics.

  6. 反強磁性体におけるスピン変換ダイナミクスの解明

    Grant number:17H05181  2017.4 - 2019.3

    日本学術振興会  科学研究費助成事業  新学術領域研究(研究領域提案型)

    森山 貴広

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    Authorship:Principal investigator 

    Grant amount:\10140000 ( Direct Cost: \7800000 、 Indirect Cost:\2340000 )

    近年「反強磁性体スピントロニクス」の研究が活発化している。本研究では特に、反強磁性秩序を有する物質系におけるスピン自由度に起因する現象をさらに掘り下げるべく、反強磁性体における局在スピン⇔伝導スピン変換ダイナミクスの解明を目的とする。
    前年度の成果として、反強磁性磁化においてもスピントルク効果が有効であることが間接的に既に示されている。本年度(平成30年度)は、実際に反強磁性体に効率よくスピン注入し、スピントルク効果により回転する反強磁性磁化方向を電気的に検出するデバイス構造を作製し、スピントルク書き込み反強磁性メモリの動作原理(書き込み・読み出し)の実証を行った。具体的には、Pt/NiOやPt/CoGd多層膜において反強磁性メモリの実証を行い、10^7A/cm^2程度の電流にて反強磁性磁化方向の制御ができることを確認し、また抵抗変化による磁化方向の読み出しが可能であることを証明した。これらは反強磁性体においても伝導スピン⇒局在スピン変換ダイナミクスが起こることを実験的に示した重要な成果であり、数件の査読論文(Physical Review Letters、Scientific Reports、等)に出版した。本年度後半では、さらに、局在スピン⇒伝導スピン変換ダイナミクスの解明を目指して、反強磁性共鳴を利用したスピンポンピング効果による伝導スピン流生実験を行った。具体的には、THz分光装置を用い、反強磁性共鳴を励起し、共鳴線幅や、電圧測定からスピンポンピング効果の実証を試みた。本成果は、現在論文投稿中である。

  7. Fabrication of antiferromagnetic structures for low energy and high speed magnetization switching technique

    Grant number:16H04487  2016.4 - 2019.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

    SEKI Takeshi

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    Authorship:Coinvestigator(s) 

    The purposes of this research project are the materials development for fast magnetization reversal with low power consumption and the elucidation of its physical mechanism by exploiting the layered structure with an antiferromagnetic structure and its magnetization dynamics. We have fabricated the artificially controlled antiferromagnetic layered structure, and have observed its antiferromagnetic dynamics. We have systematically investigated the effect of spin orbit torque acting on the artificial antiferromagnetic structure, and finally the spin orbit torque switching has been demonstrated for the artificial antiferromagnetic structure. In addition, we have achieved the low-energy resonant magnetization switching by exciting the magnetization dynamics.

  8. Investigation of interactions between spin current and antiferromagnets

    Grant number:26870300  2014.4 - 2017.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Young Scientists (B)

    Moriyama Takahiro

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    Authorship:Principal investigator 

    Grant amount:\4160000 ( Direct Cost: \3200000 、 Indirect Cost:\960000 )

    Majority of the spintronic researches has so far been dealing with ferromagnetism and much less attention has been paid to antiferromagnets. Although it has no net magnetization, its microscopic magnetic moments can in principle exhibit a similar spintronic effect as seen in ferromagnets.This proposal was particularly aiming at experimentally demonstrating the spin torque effect on antiferromagnets and showing that antiferromagnets can indeed be functional materials for spintronic devices.
    Throughout the research period, we established the quantitative measurement technique for characterizing the spin torque acting on antiferromagnets. By using this technique, we confirmed that the spin torque effect was indeed valid in antiferromagnet. We also found the magnetoresistance in antiferromagnets associated with the direction of the magnetic moments. These results pave a pathway to "antiferromagnetic spintronics".

  9. Development of Novel Spin Dynamics Devices

    Grant number:23221008  2011.5 - 2016.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (S)

    Ono Teruo, MORIYAMA Takahiro, KIM KabJin, CHIBA Daich, KOHNO Hiroshi, NAKATANI Yoshinobu, MORIYAMA Takahiro, KIM KabJin, CHIBA Daich, KOHNO Hiroshi, NAKATANI Yoshinobu

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    Authorship:Collaborating Investigator(s) (not designated on Grant-in-Aid) 

    The purpose of this project is to develop novel spin devices that utilize the current-induced spin dynamics in non-uniform spin structure, such as a magnetic domain wall and a magnetic vortex. We succeeded in demonstrating the operation of the spin devices such as domain wall memory and vortex core memory. Furthermore, we obtained unexpected results such as the observation of spin motive force in gyrating vortex core and the modulation of ferromagnetic transition temperature of Cobalt by electric field gating.

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Industrial property rights 4

  1. 磁気メモリ素子及び該磁気メモリ素子に用いる磁性材料

    森山貴広, 小野輝男, 関 剛斎, 周 偉男, 高梨弘毅

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    Applicant:京都大学、東北大学

    Application no:特願2017-132264  Date applied:2017.7

  2. Seed Layer for Perpendicular Magnetic Anisotropy (PMA) Thin Film

    Takahiro Moriyama, Yu-Jen Wang, Ru-Ying Tong

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    Applicant:Headway Technologies, Inc.

    Application no:US 13/863545  Date applied:2013

    Announcement no:pending  Date announced:2014

    A magnetic thin film deposition having PMA (perpendicular magnetic anisotropy) is a multilayered fabrication of materials having differing crystal symmetries that smoothly transition by use of a seed layer that promotes symmetry matching. An interface between layers in the deposition, such as an interface between a layer of MgO and an Fe-containing ferromagnetic layer, is a source of perpendicular magnetic anisotropy which then propagates throughout the remainder of the deposition by means of the symmetry matching seed layer.

  3. Mg Discontinuous Insertion Layer for Improving MTJ Shunt

    Takahiro Moriyama, Yu-Jen Wang, Ru-Ying Tong

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    Applicant:Headway Technologies, Inc.

    Application no:US 13/739,016  Date applied:2013

    Announcement no:US20140197504 A1  Date announced:2014

    Patent/Registration no:8981505 

    A MTJ is disclosed with a discontinuous Mg or Mg alloy layer having a thickness from 1 to 3 Angstroms between a free layer and a capping layer in a bottom spin valve configuration. It is believed the discontinuous Mg layer serves to block conductive material in the capping layer from diffusing through the free layer and into the tunnel barrier layer thereby preventing the formation of conductive channels that function as electrical shunts within the insulation matrix of the tunnel barrier. As a result, the “low tail” percentage in a plot of magnetoresistive ratio vs Rp is minimized which means the number of high performance MTJ elements in a MTJ array is significantly increased, especially when a high temperature anneal is included in the MTJ fabrication process. The discontinuous layer is formed by a low power physical vapor deposition process.

  4. ELECTROMAGNETIC WAVE DETECTION METHODS AND APPARATUS

    Takahiro Moriyama, John Q Xiao

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    Applicant:University Of Delaware

    Application no:US 12/865,182  Date applied:2008

    Announcement no:US8669762 B2  Date announced:2014

    Patent/Registration no:8669762 

    Methods and apparatus for detecting an electromagnetic wave are provided. A device for use in an electromagnetic wave detector includes a first device layer having a first contact, a second device layer having a second contact, and a tunnel barrier layer and a resonating magnetic layer formed between the first and second device layers. The resonating magnetic layer produces a spin current responsive to an electromagnetic wave that extends into the first and second device layers. A charge differential present between the first and second contacts is dependent on the spin current.

 

Teaching Experience (Off-campus) 1

  1. Condensed matter physics (Graduate level)

    Kotyo University)

 

Social Contribution 1

  1. Vice-President and Treasurer, Cornell Japanese Graduate Students and Scholars Association

    Role(s):Planner, Organizing member

    2009.9 - 2010.9

Academic Activities 2

  1. MMM2023 Program Co-Chair

    Role(s):Planning, management, etc.

    IEEE and AIPP  2023.10 - 2023.11

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    Type:Competition, symposium, etc. 

  2. The 43rd annual conference in Magnetics in Japan

    Role(s):Planning, management, etc.

    Kyoto University  2019.9

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    Type:Academic society, research group, etc.