Faculty Profiles - TANIGUCHI Hiroki

Papers - TANIGUCHI Hiroki

Division display 121 - 140 of about 323 ／ All the affair displays >>

Broad-band Micro-light-scattering Study on Stuffed-sodalite (CaxSr1-x )8 (Al O2)12 (WO4 )2 Open Access

Katayama D., Fujii Y., Koreeda A., Taniguchi H., Terasaki I.

Meeting Abstracts of the Physical Society of Japan Vol. 71 ( 0 ) page： 2553 - 2553 2016

Nonlinear Seebeck Effect in Ca2RuO4 Open Access

Toda K., Tanabe K., Taniguchi H., Okazaki R., Nakamura F., Terasaki I.

Meeting Abstracts of the Physical Society of Japan Vol. 71 page： 1859 - 1859 2016

Effects of Magnetic Fluctuation on Transport Properties in CaRu1-xScxO3 Open Access

Yamamoto T. D., Yatagai R., Tanabe K., Okazaki R., Taniguchi H., Yasui Y., Iguchi S., Sasaki T., Terasaki I.

Meeting Abstracts of the Physical Society of Japan Vol. 71 page： 1002 - 1002 2016

Transport and Magnetic Properties in CaPd3-xCuxO4(0≦x≦2.4) Open Access

Misawa K., Tanabe K., Taniguchi H., Terasaki I.

Meeting Abstracts of the Physical Society of Japan Vol. 71 page： 1000 - 1000 2016

Co-responsive dielectric materials: toward novel functionalities over optical, mechanical, and dielectric properties Open Access

Taniguchi Hiroki

Meeting Abstracts of the Physical Society of Japan Vol. 71 page： 2587 - 2588 2016

Photo-dielectric effects in reduced LaAlO3 Open Access

Nagai T., Tanabe K., Terasaki I., Kuwabara A., Taniguchi H.

Meeting Abstracts of the Physical Society of Japan Vol. 71 page： 2514 - 2514 2016

Susceptibility of Co ions doped in Ba3Zn1Ru2O9 Open Access

Hara Y., Matsushita T., Wada N., Igarashi T., Yatagai R., Tanabe K., Taniguchi H., Terasaki I.

Meeting Abstracts of the Physical Society of Japan Vol. 71 page： 1494 - 1494 2016

Effects of the Ir impurity on the thermodynamic and transport properties of Ba<inf>4</inf>Ru<inf>3</inf>O<inf>10</inf> Reviewed

Taichi Igarashi, Ryuji Okazaki, Hiroki Taniguchi, Yukio Yasui, Ichiro Terasaki

Journal of the Physical Society of Japan Vol. 84 ( 9 ) page： 094601 2015.9

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

© 2015 The Physical Society of Japan. We report the effects of Ir impurity on the physical properties of Ba4Ru3-xIrxO10 (0 ≤ x ≤ 0.5) which is composed of three face-shared RuO6 octahedra (Ru trimer). We discuss the origin of the unique electronic phase transition from paramagnetic metal to antiferromagnetic insulator at 105K in terms of hybridized orbitals of Ru 4d in the Ru trimer. From the magnetic susceptibility and the specific heat, the transition temperature is found to decrease more remarkably than is expected in typical diluted magnets and is hardly discernible at around x = 0.5, while the magnetic interaction only decreases slightly with x. This implies that the transition is not driven by magnetic interaction. In contrast, the hump due to the phase transition still remains in the Seebeck coefficient for x = 0.5, which means that the charge gap still remains as a short-range order. Since the charge gap originates from the 4d hybridization in the Ru trimer, intra-trimer charge transfer is likely to dominate the transition.

DOI： 10.7566/JPSJ.84.094601

Web of Science

Scopus

CiNii Research

Effects of the Ir Impurity on the Thermodynamic and Transport Properties of Ba4Ru3O10

Igarashi Taichi, Okazaki Ryuji, Taniguchi Hiroki, Yasui Yukio, Terasaki Ichiro

Journal of the Physical Society of Japan Vol. 84 ( 9 ) page： 94601 - 94601 2015.9

Strong anisotropy of ferroelectricity in lead-free bismuth silicate Reviewed

Daehee Seol, Hiroki Taniguchi, Jae Yeol Hwang, Mitsuru Itoh, Hyunjung Shin, Sung Wng Kim, Yunseok Kim

Nanoscale Vol. 7 ( 27 ) page： 11561 - 11565 2015.7

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

© The Royal Society of Chemistry 2015. Bismuth silicate (Bi2SiO5) was recently suggested as a potential silicate based lead-free ferroelectric material. Here, we show the existence of ferroelectricity and explore the strong anisotropy of local ferroelectricity using piezoresponse force microscopy (PFM). Domain structures are reconstructed using angle-resolved PFM. Furthermore, piezoresponse hysteresis loops and piezoelectric coefficients are spatially investigated at the nanoscale. The obtained results confirm the existence of ferroelectricity with strong c-axis polarization. These results could provide basic information on the anisotropic ferroelectricity in Bi2SiO5 and furthermore suggest its considerable potential for lead-free ferroelectric applications with silicon technologies.

DOI： 10.1039/c5nr03161c

Web of Science

Scopus

PubMed

Effects of element substitution on the pyroelectric phase transition of stuffed-tridymite-type BaZnGeO<inf>4</inf> Reviewed

Takayuki Nagai, Shinichiro Asai, Ryuji Okazaki, Ichiro Terasaki, Hiroki Taniguchi

Solid State Communications Vol. 219 page： 12 - 15 2015.7

Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD

© 2015 Elsevier Ltd. Abstract Effects of element substitution on the phase transition between different pyroelectric phases of the stuffed-tridymite-type oxide, BaZnGeO4, are examined by dielectric measurements on BaZn1-xMxGeO4 (M=Ni, Co, and Mn) with x=0.05 and 0.10. The Ni2+-substitution is found to suppress strongly the phase transition, in marked contrast to the cases of Co2+ and Mn2+ that have only subtle influences on the transition temperature. Internal distortions of MO4 tetrahedra due to the Jahn-Teller effect might play a major role in the variation of transition temperature induced by the element substitution.

DOI： 10.1016/j.ssc.2015.06.011

Web of Science

Scopus

Structural changes and microstructures of Ba<inf>1-x</inf>Sr<inf>x</inf>Al<inf>2</inf>O<inf>4</inf> for 0 < x < 0.4

E. Tanaka, Y. Ishii, H. Tsukasaki, S. Mori, M. Osada, H. Taniguchi, Y. Sato, Y. Kubota

Journal of the Korean Physical Society Vol. 66 ( 9 ) page： 1355 - 1358 2015.5

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

© 2015, The Korean Physical Society. We have investigated the structural changes and the microstructures of Ba1-xSrxAl2O4 for 0 < x < 0.4 by using transmission electron microscope (TEM) and synchrotron radiation powder X-ray diffraction experiments. The TEM experiments revealed the existence of a structural phase boundary at approximately x = 0.1, at which the superlattice reflection spots at the 1/2 0 0 -type positions change into diffuse streaks along three equivalent <110> directions in the hexagonal structure. In addition, real-space images of Ba1-xSrxAl2O4 for 0 < x < 0.4 reveal that BaAl2O4 should be characterized as a modulated structure with triple-q modulation vectors along the <110> directions and on the other hand, Ba1-xSrxAl2O4 for 0.1 < x < 0.4 be characterized as an intermediate (precursor) state with a rigid unit mode due to structural instability. These experimental results implied that the partial substitution of Sr2+ for Ba2+ should suppress a structural instability due to the AlO4 tetrahedral network and decrease the structural phase transition temperature.

DOI： 10.3938/jkps.66.1355

Web of Science

Scopus

Photo-Seebeck effect in ZnS Reviewed

Yuuka Shiraishi, Ryuji Okazaki, Hiroki Taniguchi, Ichiro Terasaki

Japanese Journal of Applied Physics Vol. 54 ( 3 ) 2015.3

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

© 2015 The Japan Society of Applied Physics. To explore the thermoelectric transport nature of photo-excited carriers, the electrical conductivity and the Seebeck coefficient are measured under ultraviolet illumination in the wide-gap semiconductor ZnS near room temperature. The conductivity increases linearly as against the photon flux density with little dependence on temperature, indicating the conduction under illumination is mostly governed by the photo-doped carriers. We have found that, in high contrast to the temperature-insensitive photoconductivity, the temperature dependence of the Seebeck coefficient is dramatically varied by illumination, which is unexplained from a simple photo-doping effect for one majority carrier. Such a distinct difference in the transport quantities is rather understood within a two-carrier model, in which only the Seebeck coefficient is strongly affected by photo-excited minority carriers. The present result is also compared with earlier reports of the photo-Hall experiments to discuss the underlying photo-transport mechanism.

DOI： 10.7567/JJAP.54.031203

Web of Science

Scopus

Non-uniform magnetic system driven by non-magnetic ion substitution in CaRu<inf>1-x</inf>Sc<inf>x</inf>O<inf>3</inf>: Two-component analysis Reviewed Open Access

Takafumi D. Yamamoto, Ryuji Okazaki, Hiroki Taniguchi, Ichiro Terasaki

Journal of the Physical Society of Japan Vol. 84 ( 1 ) page： 014708 2015.1

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

© 2015 The Physical Society of Japan. We have studied magnetic and transport properties in polycrystalline CaRu1-xScxO3 for 0 ≤ x ≤ 0.20 in order to clarify the substitution effects of a non-magnetic trivalent ion. We find that a ferromagnetic transition with Tc ~ 30K is observed in Sc-substituted samples. The composition dependence of the Curie-Weiss temperature ΘCW implies that the magnetic susceptibility has a paramagnetic contribution with negative ΘCW and a ferromagnetic contribution with positive ΘCW. The field dependence of magnetization at 2K is also understood as a summation of the ferromagnetic and paramagnetic components. These results suggest that CaRu1-xScxO3 is a non-uniform magnetic system. The relationship between the ferromagnetic ordering and the transport properties is also discussed.

DOI： 10.7566/JPSJ.84.014708

Yamamoto Takafumi D., Okazaki Ryuji, Taniguchi Hiroki, Terasaki Ichiro

Journal of the Physical Society of Japan Vol. 84 ( 1 ) page： 14708 - 14708 2015.1

Fractal Dynamics in Relaxor Ferroelectrics Studied by Broad-Band Light Scattering Spectroscopy

KOREEDA Akitoshi, FUJII Yasuhiro, TANIGUCHI Hiroki

Nihon Kessho Gakkaishi Vol. 57 ( 4 ) page： 219-225 2015

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

We report the broadband light-scattering spectroscopy of a single crystal of a prototypical relaxor ferroelectric, Pb(Mg1/3Nb2/3)O3. A self-similar, "power-law central peak" has been observed, indicating the presence of a fractal in the crystal. A strong correspondence exists between the temperature dependence of the power exponent, and that of the reported behaviors of "polar nanoregions", which consist of the fractal percolation cluster in the crystalline matrix of the material.

DOI： 10.5940/jcrsj.57.219

CiNii Research

Raman Tensor Analysis by Angle-Resolved Polarized Spectroscopy

FUJII Yasuhiro, KOREEDA Akitoshi, SHIMIZU Takao, TANIGUCHI Hiroki

Nihon Kessho Gakkaishi Vol. 57 ( 5 ) page： 285-290 2015

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

Phonon properties of lead titanate were investigated by measuring polarization-direction dependence of Raman intensities. Quantitative angle-resolved Raman spectroscopy is advantageous for detecting anisotropic nature of the sample material since that reflects the symmetry of vibrational modes. In this study, a broadband half-waveplate was utilized to establish high quantitativity, stability, and spatial reliability of the angle-resolved measurement.

DOI： 10.5940/jcrsj.57.285

CiNii Research

Ruthenium oxide as a thermoelectric material: unconventional thermoelectric properties of Li2RuO3 Reviewed

Ichiro Terasaki, Shuhei Abe, Yukio Yasui, Ryuji Okazaki, Hiroki Taniguchi

JOURNAL OF MATERIALS CHEMISTRY C Vol. 3 ( 40 ) page： 10430 - 10435 2015

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

Ruthenium oxides are typical strongly correlated electron systems, where various ordering phenomena occur through delicate interplay among the charge, spin and orbital degrees of freedom. We propose that the thermoelectric properties can be improved by controlling such ordered phases in strongly correlated electron systems. Honeycomb Ru oxide Li2RuO3 is a prime example that exhibits a unique phase transition at 540 K with a charge gap. We have found that the ordered state can be modified by substituting the Ru site partially, and succeeded in increasing the thermopower by keeping the resistivity around the same value to enhance the power factor substantially.

DOI： 10.1039/c5tc01619c

Web of Science

Ruthenium oxide as a thermoelectric material: Unconventional thermoelectric properties of Li<inf>2</inf>RuO<inf>3</inf> Reviewed

Ichiro Terasaki, Shuhei Abe, Yukio Yasui, Ryuji Okazaki, Hiroki Taniguchi

Journal of Materials Chemistry C Vol. 3 ( 40 ) page： 10430 - 10435 2015

Publishing type：Research paper (scientific journal)

© The Royal Society of Chemistry 2015. Ruthenium oxides are typical strongly correlated electron systems, where various ordering phenomena occur through delicate interplay among the charge, spin and orbital degrees of freedom. We propose that the thermoelectric properties can be improved by controlling such ordered phases in strongly correlated electron systems. Honeycomb Ru oxide Li2RuO3 is a prime example that exhibits a unique phase transition at 540 K with a charge gap. We have found that the ordered state can be modified by substituting the Ru site partially, and succeeded in increasing the thermopower by keeping the resistivity around the same value to enhance the power factor substantially.

DOI： 10.1039/c5tc01619c

Scopus

21pCJ-2 Mechanism of Ferroelectricity in Perovskite-type Oxides and Prospect for the Development of New Ferroelectric Oxides Open Access

Taniguchi Hiroki

Meeting Abstracts of the Physical Society of Japan Vol. 70 ( 0 ) page： 2698 - 2699 2015

　 PREV - NEXT 　

<TANIGUCHI Hiroki>

Papers - TANIGUCHI Hiroki