Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing  

DOI： 10.35848/1347-4065/abac40

Other Link： https://iopscience.iop.org/article/10.35848/1347-4065/abac40/pdf

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

DOI： 10.35848/1882-0786/ab8742

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1063/1.5116058

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/adma.201804004

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

The anomalous Hall effect in ferromagnets is a well-known phenomenon in which electromotive force is generated in the direction perpendicular to both the electric current and the magnetization. With nonmagnetic heavy metals, the generation of spin current by the spin Hall effect, as well as excitation of magnetization dynamics in an adjacent ferromagnet by spin-transfer torque, has been reported. However, the generation of a spin current in ferromagnets by the anomalous Hall effect has so far not been measured. Here we report the observation of spin current generation by the anomalous Hall effect through spin-transfer torque excitation in CoFeB/Cu/NiFe trilayer films. In this spin anomalous Hall effect, a spin current generated in the CoFeB by the anomalous Hall effect is injected into the NiFe and excites spin-transfer torque in the NiFe. This leads to a measurable modulation in the ferromagnetic resonance linewidth of the NiFe. The spin anomalous Hall angle in the CoFeB is estimated to be -0.14 +/- 0.05, which is comparable to the spin Hall angle reported in heavy metals.

DOI： 10.1038/s41928-018-0026-z

Web of Science

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

We have systematically investigated the Gilbert damping constant a for L1(0)-FePd films using the time-resolved magneto-optical Kerr effect (TRMOKE). The field angle dependence of TRMOKE signals was measured and analyzed. The field angle dependence of the lifetime of magnetization precession was explained by evaluating extrinsic contributions such as the anisotropy distribution and two-magnon scattering. The crystalline uniaxial perpendicular magnetic anisotropy constant K-u and alpha values were evaluated for FePd films for various L1(0) order parameters S. K-u values of approximately 15 Merg/cm(3) were obtained for films with large-S values (i.e., over 0.8). In addition, alpha for the low-S film was found to be approximately 0.007 and decreased with increasing S. Smaller values of alpha (of 0.002-0.004) were obtained for films with S values of approximately 0.6-0.8. Results revealed that FePd films have both large-K-u and small-alpha values, which is a useful property for low-power magnetization switching while maintaining high thermal stability in spin-transfer-torque magnetoresistive random access memory applications.

DOI： 10.1103/PhysRevB.94.174425

Web of Science

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

Coherent spin-wave generation by focused ultrashort laser pulse irradiation was investigated for a permalloy thin film atmicrometer scale using an all-optical space-and time-resolved magneto-opticalKerr effect microscope. The spin-wave packet propagating perpendicular to the magnetization direction was clearly observed; however, that propagating parallel to the magnetization direction was not observed. The propagation length, group velocity, center frequency, and packet width of the observed spin-wave packet were evaluated and quantitatively explained in terms of the propagation of a magnetostatic spin wave driven by the ultrafast change of an out-of-plane demagnetization field induced by the focused-pulse laser.

DOI： 10.1103/PhysRevB.94.020401

Web of Science

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

The cause of the time scale for ultrafast demagnetization induced by irradiation using a fs pulse laser remains an open issue. Spin-flip mediated by electron-phonon scattering due to spin-orbit interactions is one major theory proposed to explain ultrafast demagnetization. Ultrafast demagnetization in Ni, FePd, and FePt films was investigated in order to systematically study the influence of heavy elements on the demagnetization time. The ultrafast demagnetization in these systems was analyzed using the microscopic three temperature model, which is a theory based on spin-flip mediated by electron-phonon scattering. The spin-flip probability (a(sf)) values for the Ni, FePd, and FePt films were evaluated in the low pump fluence regime. It was found that the a(sf) value for the Ni film was larger than that for the FePd and FePt films. Thus, there is no correlation between the a(sf) value and the spin-orbit coupling strength. Fast demagnetization of the FePd film was also observed due to large electron-phonon scattering. In addition, it was found that the a(sf) values decreased with increasing magnetization quenching for all the films.

DOI： 10.1088/0022-3727/49/3/035002

Web of Science

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

Magnetization dynamics and damping for FePd films were investigated using the all-optical time-resolved magneto-optical Kerr effect. We deposited 16-nm-thick FePd thin films on a single crystal MgO(001) substrate. Both in-plane magnetic anisotropy and perpendicular magnetic anisotropy (PMA) FePd films were fabricated using the magnetron sputtering method at various substrate temperatures <i>T</i>_s. The dependencies of magnetization dynamics on the external magnetic field angle at fixed external magnetic field strengths were analyzed. The effective damping constant, <i>α</i>_eff, for FePd films with PMA exhibited anisotropy, whereas the <i>α</i>_eff for FePd with in-plane magnetic anisotropy did not depend significantly on the field angle. A uniaxial crystalline magnetic anisotropy constant, <i>K</i>_u1, of 11 Merg/cm³ and a minimum for <i>α</i>_eff of 0.007 were observed for film prepared at <i>T</i>_s = 200°C. This <i>α</i>_eff value was much smaller than that for other Fe- and Co-based materials with large PMA such as <i>L</i>1₀-FePt alloy, Co/Pt(Pd) multilayers.

DOI： 10.3379/msjmag.1501R004

CiNii Books

Other Link： https://jlc.jst.go.jp/DN/JLC/20007068766?from=CiNii

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

High-quality L1(0) ordered 20 nm-thick FePd epitaxial thin films with a large perpendicular magnetic anisotropy were fabricated using a SrTiO3 substrate. The uniaxial crystalline magnetic anisotropy constant Ku evaluated for the films annealed above 500 degrees C was 14 Merg/cm(3). A very low effective damping constant, alpha(eff) = 0.007, was observed for FePd thin films annealed at 500 degrees C. This value is smaller than that of other Fe-based ordered alloys with a large perpendicular magnetic anisotropy. (C) 2014 AIP Publishing LLC.

DOI： 10.1063/1.4897547

Web of Science

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

The magnetization dynamics of both Ta/CoFeB/MgO and Ta/CoFeB/Ta films were investigated using an all-optical pump-probe method. The magnetic field strength and the applied field direction dependencies of the precession frequency and the relaxation time were explained well by the Landau-Lifshitz-Gilbert equation when taking the magnetic anisotropy distribution in the film into account. The thickness dependence of the a values obtained for both stacked films was also discussed. The a values increased linearly with increasing inverse CoFeB thickness (t(CoFeB)). The slope of the a vs 1/t(CoFeB) characteristic for Ta/CoFeB/MgO films was smaller than that for Ta/CoFeB/Ta films, implying that the enhancement of a was caused by the CoFeB/Ta interface. Comparison of the annealing temperature dependence of a and the perpendicular magnetic anisotropy constant Ku revealed no correlation between a and Ku.

DOI： 10.1103/PhysRevB.89.174416

Web of Science

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Fast magnetization precession was observed in L1(0)-FePt thin films with different L1(0) order parameter values by all optical pump-probe technique. Precession frequency was varied widely for the films with different order parameter, which is due to large difference in perpendicular magnetic anisotropy. Gilbert damping constant (alpha) was estimated from relaxation time as apparent damping. Clear difference in alpha was not observed with different perpendicular magnetic anisotropy. (C) 2013 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.52.073002

Web of Science

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

Gilbert damping is investigated in perpendicularly magnetized CoFeB thin films using ferromagnetic resonance and time-resolved magneto-optical Kerr effect. The CoFeB films were deposited on a MgO layer and annealed at different temperatures. The lowest effective damping constant alpha(eff) values were 0.017, 0.013, and 0.009 for the films annealed at 250, 300, and 350 degrees C, respectively; these values were smaller than the values reported previously. (C) 2012 The Japan Society of Applied Physics

DOI： 10.1143/APEX.5.083001

Web of Science

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

Abstract

Physical implementation of neuromorphic computing using spintronics technology has attracted recent attention for the future energy-efficient AI at nanoscales. Reservoir computing (RC) is promising for realizing the neuromorphic computing device. By memorizing past input information and its nonlinear transformation, RC can handle sequential data and perform time-series forecasting and speech recognition. However, the current performance of spintronics RC is poor due to the lack of understanding of its mechanism. Here we demonstrate that nanoscale physical RC using propagating spin waves can achieve high computational power comparable with other state-of-art systems. We develop the theory with response functions to understand the mechanism of high performance. The theory clarifies that wave-based RC generates Volterra series of the input through delayed and nonlinear responses. The delay originates from wave propagation. We find that the scaling of system sizes with the propagation speed of spin waves plays a crucial role in achieving high performance.

DOI： 10.1038/s44306-024-00008-5

Other Link： https://www.nature.com/articles/s44306-024-00008-5

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

DOI： 10.1103/physrevresearch.5.013222

Other Link： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevResearch.5.013222/fulltext

Language：English   Publishing type：Research paper (scientific journal)  

We evaluated the self-induced spin-orbit torque (SOT) in a single ferromagnetic layer. Spin-torque ferromagnetic resonance (ST-FMR) was measured for the very thin Ni-Fe (permalloy, Py) layers with and without structural inversion symmetry: asymmetric and symmetric Py layers. For both structures, the fieldlike component coming from the Oersted field clearly appeared. On the other hand, the dampinglike component was observed only for asymmetric Py with thickness . This dampinglike torque is attributable to the significant spatial change in the properties of Py. We propose a toy model to analyze the self-induced SOT.

DOI： 10.1103/PhysRevB.104.094430

Scopus

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

DOI： 10.1063/5.0042899

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

DOI： 10.1002/smsc.202000062

Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/smsc.202000062

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AIP Publishing LLC  

DOI： 10.1063/5.0037427

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AIP Publishing LLC  

DOI： 10.1063/9.0000114

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMERICAN CHEMICAL SOCIETY  

Since it was recently demonstrated in a spin-valve structure, magnetization reversal of a ferromagnetic layer using a single ultrashort optical pulse has attracted attention for future ultrafast and energy-efficient magnetic storage or memory devices. However, the mechanism and the role of the magnetic properties of the ferromagnet as well as the time scale of the magnetization switching are not understood. Here, we investigate single-shot all-optical magnetization switching in a GdFeCo/Cu/[Co
x
Ni1-x/Pt] spin-valve structure. We demonstrate that the threshold fluence for switching both the GdFeCo and the ferromagnetic layer depends on the laser pulse duration and the thickness and the Curie temperature of the ferromagnetic layer. We are able to explain most of the experimental results using a phenomenological model. This work provides a way to engineer ferromagnetic materials for energy efficient single-shot all-optical magnetization switching.

DOI： 10.1021/acs.nanolett.0c03373

PubMed

Language：English   Publishing type：Research paper (scientific journal)  

New methods to induce magnetization switching in a thin ferromagnetic material using femtosecond laser pulses without the assistance of an applied external magnetic field have recently attracted a lot of interest. It has been shown that by optically triggering the reversal of the magnetization in a GdFeCo layer, the magnetization of a nearby ferromagnetic thin film can also be reversed via spin currents originating in the GdFeCo layer. Here, using a similar structure, it is shown that the magnetization reversal of the GdFeCo is not required in order to reverse the magnetization of the ferromagnetic thin film. This switching is attributed to the ultrafast spin current and can be generated by the GdFeCo demagnetization. A larger energy efficiency of the ferromagnetic layer single pulse switching is obtained for a GdFeCo with a larger Gd concentration. Those ultrafast and energy efficient switchings observed in such spintronic devices open a new path toward ultrafast and energy efficient magnetic memories.

DOI： 10.1002/advs.202001996

PubMed

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

DOI： 10.1103/PhysRevB.102.100403

Other Link： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.102.100403/fulltext

Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

We investigated laser-pulse-induced terahertz (THz) emission in Ta/CoFeB/Ir/CoFeB/Ta layered synthetic magnets with different Ir spacer thicknesses. THz emissions were observed under no applied magnetic fields for samples exhibiting interlayer antiferromagnetic exchange couplings, and those THz emissions also showed oscillatory behavior against the Ir spacer thicknesses. These results are qualitatively explained with the THz emission mechanism due to the inverse spin Hall effect for the laser-induced spin current in the layered structures. We also discuss the effect of a non-collinear configuration of magnetizations on THz emission with macrospin simulation.

DOI： 10.35848/1882-0786/ab88c2

Scopus

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

DOI： 10.1103/PhysRevApplied.13.044036

Other Link： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevApplied.13.044036/fulltext

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

Laser pulse induced terahertz (THz) emission from Ta/(CoxFe1-x)80B20/MgO thin films, with varying compositions x and annealing temperatures, is investigated. With increasing annealing temperature, the THz emission intensity exhibits significant dependence on x, with maxima at x of 0.1-0.3. The x dependence of the THz emission originated from the composition dependence of the spin currents induced in CoxFe1-x formed by the crystallization of amorphous CoFeB after the annealing. The origin of the laser-induced spin current is qualitatively discussed in terms of a ballistic transport of hot electrons and a spin-dependent Seebeck effect with different compositions.

DOI： 10.1103/PhysRevB.100.140406

Scopus

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

DOI： 10.1103/PhysRevB.100.144427

Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

DOI： 10.7567/JJAP.57.120302

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

Propagating spin waves excited by a micro-focused ultra-short pulse laser were investigated in Permalloy films with the thicknesses of 20, 50, and 100 nm by means of an all-optical space-and-time-resolved magneto-optical Kerr effect. Although various perpendicular standing spin-wave modes were excited, the propagating magneto-static surface spin wave was clearly detected in each film, where the group velocities of approximately 4, 8, and 12 km/s and the propagation lengths of 3.8, 6.6, and 13 mu m for the 20, 50, and 100 nm-thick films, respectively, were evaluated. The evaluated group velocities were consistent with the theoretical values, whereas the propagation lengths were smaller than the theoretical values with the Gilbert damping constant alpha of 0.008.

DOI： 10.1109/TMAG.2017.2707421

Web of Science

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

Focused pulse-laser-induced propagating magnetostatic surface spin waves (MSSWs) were investigated using an all-optical space-time-resolved magneto-optical Kerr effect microscope in 20-nm-thick permalloy thin films to clarify reciprocity and symmetry of MSSW emission. The microscope setup was constructed with variable direction of the applied magnetic field, and the corresponding angular dependence was examined. MSSWs were reciprocally emitted from the laser spot, in contrast to the nonreciprocal emission obtained by the antenna method. Specifically, the observed excitation amplitude and phase were independent of the propagation and magnetization directions within experimental error. By transforming the data into wave number-frequency space, the MSSW dispersion relation was clearly identified within the wave number of 2-3rad/mu m and frequency of 10 GHz. These observations are consistent with the model of ultrafast modulation of out-of-plane shape magnetic anisotropy inside the focused laser spot. In addition to confirming the symmetric and reciprocal emission of laser-induced MSSWs, the study demonstrated that this technique can provide all-optical microscopic spectroscopy for MSSW in metals, such as Brillouin light-scattering technique.

DOI： 10.1103/PhysRevB.96.014438

Web of Science

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

Structures and magnetic properties were systematically investigated for the monolayer (ML)-controlled Co | Ni multilayers with various Ni layer thicknesses, where the Co and Ni layers were epitaxially grown on a Al₂O₃(<inline-formula><tex-math version="MathJax"><![CDATA[\(11\bar{2}0\)]]></tex-math></inline-formula>) single crystal substrate or deposited on a thermally oxidized Si substrate. The epitaxial Co | Ni multilayers exhibited high uniaxial magnetic anisotropy energies (<italic>K</italic>_u) and low effective magnetic damping constants (α_eff), resulting in the perpendicular magnetization with low damping even for the 1 ML-Ni | 1 ML-Co multilayer. By comparing the experimental results with the first principles calculation, we found that the Ni atoms largely contributed to the perpendicular anisotropy for the Co | Ni multilayers. We also discussed the possible mechanism dominating the magnitude of α_efffor the Co | Ni multilayers based on the experiments and the calculations. The present results suggest that the epitaxial Co | Ni multilayer is a promising material to achieve high <italic>K</italic>_uand low magnetic damping simultaneously.

DOI： 10.7566/JSPJ.86.074710

CiNii Books

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

An all-optical time-resolved magneto-optical Kerr effect measurement of a micron-sized tunnel junction with a CoFeB electrode was performed. The femtosecond (fs) laser-induced magnetization precession was clearly observed at various magnetic field angles. The frequency f and relaxation time t of the magnetization precession varied with the voltage applied via a MgO barrier. The precession dynamics were in accordance with Kittel's ferromagnetic resonance mode, and the voltage- induced changes in f and t were well explained by the voltage- induced change in the perpendicular magnetic anisotropy of -36 fJ/Vm. (C) 2017 The Japan Society of Applied Physics

DOI： 10.7567/APEX.10.023002

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Mn-based hard magnets are potentially suitable for advanced ultra-high frequency spintronics applications because they exhibit the Larmor precession of magnetization at THz wave-range frequencies with low magnetic relaxation. However, the low magnetic relaxation properties are not well understood; thus, a more detailed study is necessary. In this study, magnetization precessions in L1(0) Mn1.54Ga, D0(22) Mn2.12Ga, and C38 MnAlGe epitaxial films grown on MgO substrates were investigated using an all-optical pump-probe method under a magnetic field of similar to 20 kOe. The coherent magnetization precessions at frequencies of more than 0.1, 0.2, and 0.3 THz for the C38 MnAlGe, L1(0) Mn1.54Ga, and D0(22) Mn2.12Ga films, respectively, were clearly measured. The effective damping constant for the C38 MnAlGe film was smaller than the previously reported value measured at 10 kOe by a factor of 2, whereas those showed a large angular dependence. The effective damping constants for the L1(0) Mn1.54Ga and D0(22) Mn2.12Ga films were independent of the field angle and approximately identical to the values measured at 10 kOe. Thus, it was concluded that the values for the Gilbert damping constant, a, were 0.008 and 0.012 for the L1(0) Mn1.54Ga and D0(22) Mn2.12Ga films, respectively. The possible origin of the discrepancy between the experimental and theoretical a values for these films is discussed. Published by AIP Publishing.

DOI： 10.1063/1.4961704

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Laser-induced magnetization precessional dynamics was investigated in epitaxial films of Mn3Ge, which is a tetragonal Heusler-like nearly compensated ferrimagnet. The ferromagnetic resonance (FMR) mode was observed, the precession frequency for which exceeded 0.5 THz and originated from the large magnetic anisotropy field of approximately 200 kOe for this ferrimagnet. The effective damping constant was approximately 0.03. The corresponding effective Landau-Lifshitz constant is approximately 60 Mrad/s and is comparable with those of the similar Mn-Ga materials. The physical mechanisms for the Gilbert damping and for the laser-induced excitation of the FMR mode were also discussed in terms of the spin-orbit-induced damping and the laser-induced ultrafast modulation of the magnetic anisotropy, respectively. (C) 2016 AIP Publishing LLC.

DOI： 10.1063/1.4939447

Web of Science

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/jpsgaiyo.71.1.0_1169

CiNii Books

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The laser-induced spin dynamics of FeCo in perpendicularly magnetized L1(0)-MnGa/FeCo bilayers with ferromagnetic and antiferromagnetic interfacial exchange coupling ( IEC) are examined using the time-resolved magneto-optical Kerr effect. We found a precessional phase reversal of the FeCo layer as the IEC changes from ferromagnetic to antiferromagnetic. Moreover, a precession-suspension window was observed when the magnetic field was applied in a certain direction for the bilayer with ferromagnetic IEC. Our observations reveal that the spin dynamics modulation is strongly dependent on the IEC type within the Landau-Lifshitz-Gilbert depiction. The IEC dependence of the precessional phase and amplitude suggests the interesting method for magnetization dynamics modulation. (C) 2015 AIP Publishing LLC.

DOI： 10.1063/1.4936598

Web of Science

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

Spin dynamics excited by spin-polarized current in magnetic tunnel junctions (MTJs) is potentially useful in nanoscale electrical oscillation sources and detection devices. A spin oscillator/detector should work at a high frequency, such as that of a millimeter-wave, where the quality of a semiconductor device is restricted by carrier mobility, the CR time constant, and so on. Developers of spin systems for practical use need to find out how to excite spin dynamics (i) in the millimeter-wave region, (ii) with low power consumption (ex: no external magnetic field, low damping material), and (iii) for broad frequency modulation. Here L1(0)-ordered FePd alloy with perpendicular magnetocrystalline anisotropy (PMA) and a low damping constant, 0.007, was used for the free layer in the MTJs, and a homodyne-detected ferromagnetic resonance (FMR) signal was obtained at around 30 GHz together with the possibility of one-octave frequency modulation. The FMR signal in out-of-plane magnetized L10-ordered FePd free layer could be excited without an external magnetic field by injecting in-plane spin polarized alternating current. This study shows the potential utility of L1(0)-ordered alloy materials such as FePt, CoPt, MnAl, and MnGa in a variety of millimeter-wave spin devices.

DOI： 10.1021/nl504114v

Web of Science

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/jpsgaiyo.70.2.0_846

CiNii Books

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The precessional magnetization dynamics of L1(0) MnGa/Fe bilayers with a large perpendicular magnetic anisotropy are investigated using vector network analyzer ferromagnetic resonance (VNA-FMR) and time-resolved magneto-optical Kerr effect (TRMOKE). The MnGa/Fe(1 nm) bilayer exhibited perpendicular magnetization and MnGa/Fe(2 and 5 nm) bilayers showed in-plane magnetizations. The VNA-FMR and TRMOKE data for these bilayers are well explained from calculations, based on the coupled Landau-Lifshitz equations, taking into account the interfacial exchange coupling of 2.4 erg/cm(2). (C) 2014 AIP Publishing LLC.

DOI： 10.1063/1.4868087

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

We investigated the static and dynamic magnetic properties of thin films of Mn-Co-Ga Heusler compound. Gilbert damping and exchange stiffness constants of the films were evaluated by using the ferromagnetic resonance technique in the X-band regime (f = 9.4 GHz). By analyzing the experimental spectra, magnetic parameters of the films such as the line width and the Gilbert damping were deduced, and the exchange stiffness constant was estimated from the perpendicular standing spin-wave resonance. The Gilbert damping constant was estimated to be 0.017 in a specific film composition. The exchange stiffness constant showed a linear dependence on the film composition. (C) 2014 AIP Publishing LLC.

DOI： 10.1063/1.4864250

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

We studied on the magnetic damping constants (alpha) for L1(0)-FeNi and disordered FeNi employing three kinds of measurement methods. An L1(0)-FeNi thin film exhibited high perpendicular magnetic anisotropy of 7.1 x 10(6) erg cm(-3). At magnetic fields (H) lower than 2 kOe, alpha was estimated to be 0.091 +/- 0.003. However, it was reduced down to 0.013 +/- 0.001 with H, indicating that extrinsic contributions enhance alpha. The intrinsic alpha = 0.013 +/- 0.001 was comparable to alpha = 0.009 +/- 0.002 for the disordered FeNi. This suggests that L1(0)-FeNi is a candidate achieving high magnetic anisotropy and low magnetization damping simultaneously. (C) 2013 AIP Publishing LLC.

DOI： 10.1063/1.4845035

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The effects of Mg metallic interlayer on the magnetic properties of thin CoFeB films in MgO/Mg (t(Mg))/CoFeB (1.2nm)/Ta structures were studied in this letter. Our experimental result shows that the CoFeB film exhibits perpendicular magnetic anisotropy (PMA) when the CoFeB and MgO layers are separated by a metallic Mg layer with a maximum thickness of 0.8 nm. The origin of PMA was discussed by considering the preferential transmission of the Delta(1) symmetry preserved by the Mg interlayer in crystallized MgO/Mg/CoFeB/Ta. In addition, the thin Mg interlayer also contributes to enhancing the thermal stability and reducing the effective damping constant and coercivity of the CoFeB film. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4754118]

DOI： 10.1063/1.4754118

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Structural and magnetic properties of MnAl thin films with different composition, growth temperature, and post-annealing temperature were investigated. The optimum condition for fabrication of L1(0)-MnAl perpendicularly magnetized thin film deposited on Cr-buffered MgO single crystal substrate was revealed. The results of x ray diffraction indicated that the MnAl films annealed at proper temperature had a (001)-orientation and L1(0)-ordered structure. The L1(0)-ordered films were perpendicularly magnetized and had a large perpendicular anisotropy. In addition, low surface roughness was achieved. For the optimized fabrication condition, the saturation magnetization M-s of 600 emu/cm(3) and perpendicular magnetic anisotropy K-u of 1.0 x 10(7) erg/cm(3) was obtained using the Mn48Al52 target at deposition temperature of 200 degrees C and post-annealing temperature of 450 degrees C. (C) 2012 American Institute of Physics. [doi:10.1063/1.3676428]

DOI： 10.1063/1.3676428

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Fast magnetization precession is observed in L1(0)-FePt alloy epitaxial thin films excited and detected by all-optical means. The precession frequency varies from 45 to 65 GHz depending on the applied magnetic field strength and direction, which can be explained by a uniform precession model taking account of first- and second-order uniaxial magnetic anisotropy. The lowest effective Gilbert damping constant has a minimum value of 0.055, which is about half that in Co/Pt multilayers and is comparable to Ni/Co multilayers with perpendicular magnetic anisotropy. (C) 2011 American Institute of Physics. [doi:10.1063/1.3549704]

DOI： 10.1063/1.3549704

Web of Science

Event date： 2022.11

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

Event date： 2022.10

Language：English   Presentation type：Poster presentation  

Event date： 2022.9

Language：Japanese   Presentation type：Poster presentation  

Event date： 2022.9

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

Event date： 2022.8

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

Event date： 2022.7

Language：English   Presentation type：Oral presentation (general)  

Event date： 2022.3

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

Venue：ハイブリッド(青山学院大学)  

Event date： 2021.12

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

Event date： 2021.10

Language：English   Presentation type：Poster presentation  

Event date： 2021.9

Language：Japanese   Presentation type：Poster presentation  

Event date： 2021.9

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

Event date： 2021.6

Language：Japanese  

Event date： 2021.4

Language：English   Presentation type：Oral presentation (general)  

Event date： 2020.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：Tohoku Univ.  

Event date： 2020.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Online  

Event date： 2019.11

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

Venue：Las vegas, USA  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：Online  

Language：English   Presentation type：Oral presentation (general)  

Language：English   Presentation type：Poster presentation  

Language：English   Presentation type：Poster presentation  

Venue：Las vegas, USA  

Language：English   Presentation type：Poster presentation  

Venue：Yokohama  

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

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：Waseda University  

Language：English   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Poster presentation  

Presentation type：Poster presentation  

Language：English   Presentation type：Poster presentation  

Language：English   Presentation type：Poster presentation  

Language：English   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Poster presentation  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：English   Presentation type：Poster presentation  

Language：English   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Poster presentation  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (invited, special)  

Venue：Institut Jean Lamour, Nancy, France  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：English   Presentation type：Poster presentation  

Venue：Nancy, France  

Language：English   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Poster presentation  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：Online  

Language：English   Presentation type：Poster presentation  

Venue：Chiba  

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

Venue：Nancy, France  

Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Poster presentation  

Venue：Waseda University  

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

Venue：Purdue University  

Presentation type：Oral presentation (general)  

Language：English   Presentation type：Oral presentation (general)  

Venue：Nancy, France  

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

Language：Japanese  

Language：Japanese   Presentation type：Poster presentation  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：AIMR, Tohoku Univ.  

Language：English   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：English   Presentation type：Poster presentation  

Language：English   Presentation type：Poster presentation  

Venue：Sendai  

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

Venue：Danang, Vietnum  

Language：English   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Poster presentation  

Language：Japanese   Presentation type：Poster presentation  

Language：English   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン  

Language：Japanese   Presentation type：Poster presentation  

Presentation type：Oral presentation (invited, special)  

Venue：日本大学、千葉  

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

Venue：横浜国立大学, 神奈川  

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

Presentation type：Oral presentation (invited, special)