研究者詳細 - 小山　佳一

論文 - 小山　佳一

分割表示 496 件中 301 - 320 件目／全件表示 >>

V. Provenzano, B. Baumgold, R.D. Shull, A.J. Shapiro, K. Koyama, K. Watanabe, N.K. Singh, K.G. Suresh, A.K. Nigam, S.K. Malik . Structure and magnetocaloric properties of the Fe-doped HoTiGe alloy . J. Appl. Phys.99 08K906 2006年査読

F. Ishikawa, K. Koyama, K. Watanabe, T. Asano, and H. Wada . First-order phase transition at the Curie temperature in MnAs and MnAs0.9Sb0.1 . J. Phys. Soc. Jpn75 84604 2006年査読

H. Yabuta, K. Umeo, T. Takabatake, K. Koyama and K. Watanabe . Temperature- and field-induced first-order ferromagnetic transitions in MnFe(P1-xGex) . J. Phys. Soc. Jpn75 113707 2006年査読

K. Koyama, H. Okada, K. Watanabe, T. Kanomata, R. Kainuma, W. Ito, K. Oikawa, K. Ishida . Observation of large magnetoresistance of magnetic Heusler alloy Ni50Mn36Sn14 in high magnetic fields . Appl. Phys. Lett.89 182510 2006年査読

K. Koyama, T. Kanomata, R. Kainuma, K. Oikawa, K. Ishida and K. Watanabe, . High field X-ray diffraction measurements of novel ferromagnetic shape-memory alloy Ni50Mn36Sn14 . Physica B383 24 - 26 2006年査読

K. Koyama, K. Watanabe, T. Kanomata, R. Kainuma, K. Oikawa, and K. Ishida . Observation of field-induced reverse transformation in ferromagnetic shape memory alloy Ni50Mn36Sn14 . Appl. Phys. Lett.88 132505 2006年査読

V.A. Chernenko, V.A. Lvov, T. Kanomata, T. Kakeshita, K. Koyama and S. Besseghini . Martensitic transformation in Ni-Mn-Ga alloy under high magnetic fields . Mater. Trans.47 635 - 638 2006年査読

K. Koyama, T. Kanomata, T. Watanabe, T. Suzuki, H. Nishihara, and K. Watanabe . X-ray powder diffraction studies of Mn3Ga0.97Al0.03C in magnetic fields . Mater. Trans. 47 492 - 495 2006年査読

K. Yagasaki, S. Notsu, Y. Takaesu, T. Nakama, E. Sakai, K. Koyama, K. Watanabe and A.T. Burkov . X ray diffraction on rare earth-3d Laves phase compound of ErCo2 in magnetic field . Physica B378-380 1089 - 1090 2006年査読

S.V. Demishev, A.V. Semeno, A.A. Pronin, N.E. Sluchanko, N.A. Samarin, H. Ohta, S. Okubo, M. Kimata, K. Koyama, M. Motokawa and A.V. Kuznetsov . Low-temperature study of the quantum critical phenomena in CuGeO3:Fe . J. Magn. Magn. Matter.300 e346 - e349 2006年査読

M. Kimata, H. Ohta, K. Koyama, M. Motokawa, R. Kondo, S. Kagoshima, H. Tanaka, M. Tokumoto, H. Kobayashi, and A. Kobayashi . Fermi surface study of organic conductors using a magneto-optical measurement under high magnetic fields . J. Phys.: Conf. Ser.51 359 - 362 2006年査読

M. Kimata, Y. Oshima, K. Koyama, H. Ohta, M. Motokawa, H. Nishikawa, K. Kikuchi, I. Ikemoto . Detailed fermi surface topology of the quasi-one-dimensional conductor (DMET)2I3 . J. Low Temp. Phys.142 523 - 526 2006年査読

H. Kato, T. Akiya, M. Sagawa, K. Koyama, T. Miyazaki . Field-induced alignment of Nd-rich phase and coercivity in sintered Nd-Fe-B magnets . INTERMAG 2006 - IEEE International Magnetics Conference 914 2006年

Hironari Okada, Keiichi Koyama, Kazuo Watanabe . Specific heat measurement of the spinel compound CuV2S4 . LOW TEMPERATURE PHYSICS, PTS A AND B850 1317 - + 2006年査読

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：AMER INST PHYSICS

We have performed specific heat measurements of a high-quality polycrystalline sample of CuV2S4. Two anomalies associated with charge density wave (CDW) transitions are clearly observed at T-t1 = 92 K and T-t2h = 58 K. The anomalies at T-t1 and T-t2h show lambda-type and spike-shaped behavior, indicating second and first order phase transitions, respectively. The electronic specific heat coefficient gamma and the Debye temperature Theta(D) are estimated to be 36 mJ/moIK(2) and 347 K, respectively. gamma of CuV2S4 is much larger than that of CuTi2S4, whereas CuTi2S4 exhibits a CDW gap at low temperature. This enhancement of gamma is probably attributed not only to the electron-phonon interaction but also to electron-electron interactions.

DOI： 10.1063/1.2355192

Web of Science

A. Himori, S. Ohishi, K. Koyama, K. Watanabe, T. Shigeoka . Multistep metamagnetism of NdRh2Ge2 single crystal . YAMADA CONFERENCE LX ON RESEARCH IN HIGH MAGNETIC FIELDS51 63 - + 2006年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IOP PUBLISHING LTD

Measurements of high-field magnetization up to 18 T, magnetic susceptibility and specific heat have been performed on a tetragonal NdRh2Ge2 single crystal and polycrystalline sample. From the temperature dependences of magnetic susceptibilities, this compound shows an antiferromagnetic behaviour with Neel temperature of 50 K. Another magnetic transition is observed at 37 K. At low temperatures, a multi-step metamagnetic behaviour is observed along the easy c-axis and a strong magnetic anisotropy is seen. The saturation magnetic moment is estimated to be 2.76 mu(B)/f.u.. There are five magnetic phases below the induced ferromagnetic phase in the H-T magnetic phase diagram. To discuss the magnetic behaviours, the CEF analysis has been made.

DOI： 10.1088/1/1742-6596/51/1/012

Web of Science

Scopus

T. Hori, K. Koyama, H. Shiraishi, K. Watanabe . Magnetic properties of Nd(x)Erl(1-x)Mn(6)Sn(6) alloys . YAMADA CONFERENCE LX ON RESEARCH IN HIGH MAGNETIC FIELDS51 47 - + 2006年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IOP PUBLISHING LTD

We have conducted low- and high-field magnetization measurements and neutron diffraction experiments on NdxEr1-xMn6Sn6 alloys (0 <= x <= 0.5) with hexagonal MgFe6Ge6 type structure. The alloy with x = 0.1 shows a complex helical antiferromagnetism with the magnetic moments rotating in the c plane below the Curie temperature T-C = 340 K, and a ferrimagnetism below the temperature T-t = 100 K. In the ferrimagnetic state, the magnetic moments mu(Mn) and mu(Nd) are parallel to each other, and antiparallel to mu(Er). The alloy with x = 0.4 shows also a similar ferrimagnetic structure below the Curie temperature T-C = 360 K. It is likely that the each magnetic moments are keep a constant values of mu(Mn) = 2.3 mu(B)/Mn atom, mu(Nd) = 3 mu(B)/Nd atom and mu(Er) = 9 mu(B)/Nd atom at 10 K in the whole composition (0 < x <= 0.5). The ferrimagnetic arrangements for the alloys with 0.2 <= x <= 0.5 are not almost disturbed by magnetic field up to 26 T at 4.2 K.

DOI： 10.1088/1/1742-6596/51/1/008

Web of Science

Scopus

A. V. Andreev, E. Santava, Y. Homma, K. Koyama, T. Yamamura, Y. Shiokawa . Magnetic anisotropy of U2Co17-xSix single crystals. . Recent Advances in Actinide Science, May, I.; Alvares, R.; Bryan, N., Eds. The Royal Society of Chemistry: Cambridge 758 - 760 2006年査読

A. V. Andreev, K. Koyama, N. V. Mushnikov, V. Sechovsky, Y. Shiokawa, I. Satoh, K. Watanabe . Interplay between effects of external pressure and dilution of the U-sublattice in UCoAl-based materials: the U0.94Y0.06CoAl case . High Pressure Research26 ( 4 ) 475 - 478 2006年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

Substitution of Y for U in the itinerant 5f-electron metamagnet, UCoAl, transforms the system to a ferromagnetic state. Application of external hydrostatic pressure above 0.3GPa suppresses the spontaneous ferromagnetism and restores the paramagnetism with field-induced transition to ferromagnetic state. However, the transition becomes of the second order instead of the first-order one in parent UCoAl. © 2006 Taylor &amp
Francis.

DOI： 10.1080/08957950601103973

Scopus

H. Kato, K. Koyama, T. Miyazaki . Effect of high-magnetic-field annealing on the magnetic properties of Nd-Co-B nanocomposite ribbons . INTERMAG ASIA 2005: Digests of the IEEE International Magnetics Conference 167 2005年12月

M. Kimata, Y. Oshima, K. Koyama, H. Ohta, M. Motokawa, H. M. Yamamoto, R. Kato . Fermi surface study of β′′-(BEDT-TTF)(TCNQ) by magnetooptical measurements . Synthetic Metals153 ( 1-3 ) 369 - 372 2005年9月

記述言語：英語掲載種別：研究論文（学術雑誌）

We have performed magnetooptical measurements of β′′-(BEDT-TTF)(TCNQ) using a cavity perturbation technique with a millimeter vector network analyzer (MVNA) and a 14 T superconducting magnet at IMR, Tohoku University. The results of ADMRO and SdH measurements at low temperatures are not consistent with the band calculation result. Therefore, we are interested in Fermi surfaces at low temperatures and have performed magnetooptical measurements of β′′-(BEDT-TTF)(TCNQ). Although the band calculation and ADMRO results suggest the existence of Q1D FS, our results suggest the existence of Q2D FS only. From the results of magnetooptical measurements, we discuss the FS topology of this system at low temperatures. © 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.synthmet.2005.07.308

Web of Science

Scopus

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