研究者詳細 - 小山　佳一

論文 - 小山　佳一

分割表示 496 件中 121 - 140 件目／全件表示 >>

T. Tsutaoka, K. Obata, S. Cheyvuth and K. Koyama . Magnetic phase transitions in Er7Rh3 studied on single crystals . J. Alloy Comp.606 214 - 218 2014年査読

S. Mondal, J.L.Her, K. Koyama, and T.M Pan . Resistive switching behavior in Lu2O3 thin film for advanced flexible memory applications . Nanoscale Research Lett.9 3 2014年査読

Pan T., Chen F., Hung M., Her J., Koyama K. . Structural properties and electrical characteristics of high-κ Tm2O3 gate dielectrics for InGaZnO thin film transistors . Science of Advanced Materials6 ( 9 ) 1973 - 1978 2014年

記述言語：日本語出版者・発行元：Science of Advanced Materials

In this paper, we studied the structural properties and electrical characteristics of high-dielectric constant (high-κ) Tm<inf>2</inf>O<inf>3</inf> gate dielectrics for amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) applications. We used X-ray diffraction to determine the growth directions and crystallinity of the Tm<inf>2</inf>O<inf>3</inf> films, X-ray photoelectron spectroscopy to analyze the chemical structure of the films, and to monitor the morphological feature of the Tm<inf>2</inf>O<inf>3</inf> films after annealing at various temperatures. The high-κ Tm<inf>2</inf>O<inf>3</inf> a-IGZO TFT annealed at 400°C exhibited a lower threshold voltage of 1.68 V, a higher field effect mobility of 11.8 cm<sup>2</sup>/V-s, a larger I<inf>on</inf>/I<inf>off</inf> ratio of 3.9×107, and a smaller SS of 420 mV/dec., relative to those of the systems that had been subjected to other annealing conditions. This result suggests the Tm<inf>2</inf>O<inf>3</inf> film featuring a higher dielectric constant as well as a smoother surface. The V<inf>TH</inf> stability on high-κ Tm<inf>2</inf>O<inf>3</inf> IGZO TFTs was also explored under positive bias stress.

DOI： 10.1166/sam.2014.1963

Scopus

Kakimoto T., Goto J., Fujii S., Koyama K., Ishida S. . Electronic and Magnetic Properties of Mn₂Sb₁₋xAs[x] (x = 0, 0.5, 1) . MATERIALS TRANSACTIONS55 ( 12 ) 1878 - 1884 2014年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：公益社団法人日本金属学会

The electronic and magnetic properties of Mn2Sb1-xAsx (where x = 0, 0.5, 1) are investigated from first-principles total-energy calculations. The predicted magnetic ground states (ferrimagnetism for x = 0 and antiferromagnetism for x = 1) are in agreement with experimental observations; however, this is not the case for x = 0.5. Here, it is found that the artificial change of the surrounding atoms of Mn stabilizes the antiferromagnetism. A similar change stabilizes ferrimagnetism (antiferromagnetism) for x = 1 (x = 0). These results indicate that the environment around the Mn atoms plays a very important role in the stabilization of antiferromagnetism in the Mn2Sb1-xAsx system. In addition, an analysis of the sign of an effective exchange interaction as a function of the distance between the Mn atoms is performed.

DOI： 10.2320/matertrans.m2014251

Web of Science

Scopus

CiNii Research

Mitsui Y., Koyama K., Oikawa K., Watanabe K. . Magnetic field effect on the liquidus boundary of Bi-Mn binary system . AIP Conference Proceedings1618 269 - 272 2014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：AIP Conference Proceedings

The magnetic field effect (MFE) on liquidus boundary of Bi-Mn binary system was investigated by differential thermal analysis (DTA) and the computer coupling of phase diagram method (CALPHAD). The liquidus boundary for Bi-18at.%Mn and Bi-24at.%Mn rose clearly by the application of the magnetic fields. The MFE for liquidus boundary temperature Tliq changed from ΔTliq∞B2 to ΔTliq∞B because of the large increase of the peritectic temperature from BiMn and BiMn1.08 by the application of magnetic field.

DOI： 10.1063/1.4897725

Web of Science

Scopus

Abematsu K., Umetsu R., Kainuma R., Kanomata T., Watanabe K., Koyama K. . Structural and magnetic properties of magnetic shape memory alloy Ni <inf>46</inf>Mn<inf>41</inf>In<inf>13</inf> under magnetic fields . MATERIALS TRANSACTIONS55 ( 3 ) 477 - 481 2014年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：公益社団法人日本金属学会

The structural and magnetic properties of Heusler alloy Ni 46Mn41In13 were studied by magnetization and X-ray powder diffraction measurements in the 4.5350K temperature range and in magnetic fields up to 5 T. The alloy undergoes martensitic transformation from a L21-type cubic structure with ac = 0.600nm at 293K to a six-layered monoclinic (6M) structure in the transition temperature of 160230 K. The lattice parameters for the 6M structure were estimated to be am = 0.441 nm, bm = 0.557 nm, cm = 1.30 nm, αm = 90.0°, βm = 94.0°, and γm = 90.0° at 75 K. In this transformation from the L21 to 6M structures, the cell volume contracts by 0.34% at 8K. In addition, we observed the magnetic field-induced reverse transformation of this alloy. © 2014 The Japan Institute of Metals and Materials.

DOI： 10.2320/matertrans.m2013372

Web of Science

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CiNii Research

Chen C., Her J., Pan T., Chiu F., Koyama K. . Structural properties and electrical characteristics of high-k GdTiO<inf>3</inf> gate dielectrics for InGaZnO thin-film transistors . 2014 10th International Vacuum Electron Sources Conference, IVESC 2014 and 2nd International Conference on Emission Electronics, ICEE 2014 - Proceedings 2014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：2014 10th International Vacuum Electron Sources Conference, IVESC 2014 and 2nd International Conference on Emission Electronics, ICEE 2014 - Proceedings

We investigated the structural properties and electrical characteristics of GdTiO3 dielectrics for IGZO TFT devices. We used XRD, XPS, and AFM to examine the structural, compositional, and morphological features of the GdTiO3 film, respectively. The IGZO TFT featuring a GdTiO3 gate dielectric exhibited a large field-effect mobility of 32.3 cm2/V-s, a small threshold voltage of 0.14 V, a high Ion/Ioff current ratio of 4.2 × 108, and a low subthreshold swing of 213 mV/decade.

DOI： 10.1109/IVESC.2014.6891962

Web of Science

Scopus

M. Mitsui, R.Y. Umetsu, M. Saito, K. Koyama, H. Kawarada . Synthesis and diffusion of MnBi in high magnetic fields . The International Symposium on Ecotopia Science 2013 and The 5th International Symposium on Advanced Materials Development and Integration of Novel Structural Metallic and Inorganic Materials (ISETS’13 and AMDI-4) 1317 2013年12月

J. Goto, T. Kakimoto, S. Fujii and K. Koyama . Magnetic and electronic structures and Cobalt or Copper substituted Mn2Sb . Mater. Trans.54 ( 12 ) 2309 - 2312 2013年12月査読

後藤純哉、柿本貴俊、藤井伸平、小山佳一 . Electronic and magnetic structures of Cobalt substituted Mn2Sb . 日本金属学会誌77 ( 10 ) 461 - 465 2013年10月査読

Andreev A.V., Tereshina E.A., Gorbunov D.I., Šantavá E., Šebek J., Žáček M., Homma Y., Shiokawa Y., Satoh I., Yamamura T., Komatsubara T., Watanabe K., Koyama K. . Magnetic Anisotropy in Intermetallic Compounds Containing Both Uranium and 3d-Metal1 . Physics of Metals and Metallography114 ( 9 ) 727 - 733 2013年9月

記述言語：日本語出版者・発行元：Physics of Metals and Metallography

Magnetic properties of intermetallic compounds containing both uranium and a 3d metal (Fe, Co) are summarized and discussed. It was shown that the ordered magnetism of the U and 3d-metal sub- lattices can coexist in the same compound (e.g. with 2-17 and 1-12 stoichiometries) even at room and ele- vated temperatures. © Pleiades Publishing, Ltd., 2013.

DOI： 10.1134/S0031918X13090020

Scopus

Y. Mitsui, K. Oikawa, K. Koyama and K. Watanabe . Thermodynamic assessment for the Bi-Mn binary phase diagram in high magnetic fields . J. Alloys Comp.577 315 - 319 2013年8月査読

Y. Mitsui, Y. Ikehara, K. Watanabe, E.S. Choi, E.C. Palm and K. Koyama . Thermal analysis on MnBi in high magnetic fields up to 45 T . J. Korean Phys. Soc.62 1769 - 1772 2013年8月査読

Shimada D., Orihashi H., Mitsunaga D., Ito M., Hiroi M., Koyama K., Onodera R., Takahashi K., Matsubayashi K., Uwatoko Y. . Magnetic properties of Mn<inf>2</inf>Sb<inf>1-x</inf>Ge<inf>x</inf> (0.05 ≤ x ≤ 0.2) in high magnetic fields . Journal of the Korean Physical Society63 ( 3 ) 747 - 750 2013年8月査読

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of the Korean Physical Society

Magnetization and electrical resistivity measurements were carried out for polycrystalline Mn2Sb1-xGex (0.05 ≤ x ≤ 0.2) in magnetic fields up to 16 T in the 4.2 - 600 K temperature range in order to investigate the magnetic and the electrical properties under high magnetic fields. Mn2Sb0.92Ge0.08 showed a Curie temperature, T C, of 532 K and a first order magnetic transition from a ferrimagnetic (FRI) to an antiferromagnetic (AFM) phase at T t = 230 K with decreasing temperature in a zero magnetic field. With increasing x, T C decreased and T t increased. For Mn2Sb0.92Ge0.08, a matamagnetic transition from an AFM to a FRI phase was observed at 215 K. The magnetic phase diagram of Mn2Sb1-xGex is presented. © 2013 The Korean Physical Society.

DOI： 10.3938/jkps.63.747

Web of Science

Scopus

R. Onodera, S. Kimura, K. Watanabe, Y. Yokoyama, A. Makino and K. Koyama . Isothermal Crystallization of Iron-Based Amorphous Alloys in a High Magnetic Field . Mater. Trans54 ( 7 ) 1232 - 1235 2013年7月査読

A.V. Andreev, E.A. Tereshina, D.I. Gorbunov, E. Santava, J. Sebek, M. Zacek, Y. Homma, Y. Shiokawa, I. Satoh, t. Yamamura, T. Komatsubara, K. Watanabe and K. Koyama . Magnetic anisotropy in intermetallic compounds containing both Uranium and 3d-metal . Phys. Metals and Metallography114 727 - 733 2013年7月査読

T. Shigeoka, T. Fujiwara, K. Koyama, S. Kimura and K. Watanabe . Multi-step metamagnetic processes of PrPd2Si2 single crystal . J. Korean Phys. Soc.63 567 - 570 2013年7月査読

Y. Adachi, T. Kitai, K. Koyama, H. Yoshika, and T. Kaneko . Magnetization curves of TbZn2 in high magnetic fields . J. Korean Phys. Soc.62 2077 - 2079 2013年7月査読

M. Hiroi, K. Uchida, I. Shigeta, M. Ito and K. Koyama . Antiferromagnetic transition in Ru2CrSi in magnetic fields . J. Korean Phys. Soc.62 2068 - 2072 2013年7月査読

D. Shimada, H. Orihashi, D. Mitsunaga, M. Ito, M. Hiroi, K. Koyama, R. Onodera, K. Takahashi, K. Matsubayashi, Y. Uwatoko . Magnetic properties of Mn2Sb1-xGex (0.05 ? x ? 0.2) in high magnetic fields . J. Korean Phys. Soc.62 747 - 750 2013年7月査読

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