1.

論文(リポジトリ)

論文(リポジトリ)
藤井, 岳 ; 土田, 龍太郎 ; 與儀, 護 ; 辺土, 正人 ; 仲間, 隆男 ; Fujii, Gaku ; Tsuchida, Ryutaro ; Yogi, Mamoru ; Hedo, Masato ; Nakama, Takao
出版情報: 琉球大学教職センター紀要 = Bulletin of Center for Professional Development of Teachers.  pp.141-148,  2021-03-31.  琉球大学教職センター
URL: http://hdl.handle.net/20.500.12000/48021
概要: 新型コロナウィルス感染対策のため,理学部物理系の専門実験科目の授業をICTを使い遠隔で行った.一部の実験課題は動画を配信し,その動画で実験データを学生自ら取得する遠隔実験を行った. 遠隔実験について学生にアンケートを取った結果,動画による実 験に対しては肯定的な意見が多かったが, その場で質問し対応してもらえないことに不満を持つ学生がいることがわかった. すべての課題に学生が主体性をもって参加できるような教材の開発や取り組みを工夫し, さらに学生の質問等に即応できる簡便で使いやすいシステムの構築が必要である. 続きを見る
2.

論文(リポジトリ)

論文(リポジトリ)
Feng, Yejun ; Wang, Yishu ; Silevitch, D. M. ; Yan, J. -Q. ; Kobayashi, Riki ; Hedo, Masato ; Nakama, Takao ; Onuki, Yoshichika ; Suslov, A. V. ; Mihaila, B. ; Littlewood, P. B. ; Rosenbaum, T. F.
出版情報: Proceedings of the National Academy of Sciences of the United States of America.  116  pp.11201-11206,  2019-06-04.  National Academy of Sciences
URL: http://hdl.handle.net/20.500.12000/47031
概要: The magnetoresistance (MR) of a material is typically insensitive to reversing the applied field direction and varies quadratically with magnetic field in the low-field limit. Quantum effects, unusual topological band structures, and inhomogeneities that lead to wandering current paths can induce a cross-over from quadratic to linear MR with increasing magnetic field. Here we explore a series of metallic charge- and spin-density-wave systems that exhibit extremely large positive linear MR. By contrast to other linear MR mechanisms, this effect remains robust down to miniscule magnetic fields of tens of Oersted at low temperature. We frame an explanation of this phenomenon in a semiclassical narrative for a broad category of materials with partially gapped Fermi surfaces due to density waves. 続きを見る
3.

論文(リポジトリ)

論文(リポジトリ)
太田, 譲二 ; 仲村, 大 ; 辺土, 正人 ; 仲間, 隆男 ; Ota, Jouji ; Nakamura, Dai ; Hedo, Masato ; Nakama, Takao
出版情報: 琉球大学理学部紀要 = BULLETIN OF THE FACULTY OF SCIENCE UNIVERSITY OF THE RYUKYUS.  pp.33-41,  2018-09-28.  琉球大学理学部
URL: http://hdl.handle.net/20.500.12000/42785
概要: We have developed a measurement system for the electrical resistivity and thermopower using the programming language of Python on “Raspberry Pi”, a compact computer for education. The measurement equipments are connected to “Raspberry Pi” by the general purpose serial interface bus (USB), which make it possible to operate on PC with the other operating systems of Linux, Windows, and MacOS almost without modification of the measurement program. This ensures the compatibility of measurement system and the unified maintenance and management. 続きを見る
4.

論文(リポジトリ)

論文(リポジトリ)
仲村, 大 ; 辺土, 正人 ; 高江洲, 義尚 ; 内間, 清晴 ; 矢ヶ崎, 克馬 ; 仲間, 隆男 ; 藤原, 哲也 ; 繁岡, 透 ; Nakamura, Dai ; Hedo, Masato ; Takaesu, Yoshinao ; Uchima, Kiyoharu ; Yagasaki, Katsuma ; Nakama, Takao ; Fujiwara, Tetsuya ; Shigeoka, Toru
出版情報: 琉球大学理学部紀要 = Bulletin of the College of Science. University of the Ryukyus.  pp.1-8,  2011-03.  琉球大学理学部
URL: http://hdl.handle.net/20.500.12000/21887
概要: We have developed a set-up with modified "seesaw heating method" for the simultaneous measurement of thermopow er S and electrical resistivity р under hydrostatic pressures P up to 3 GPa at the temperature range between 1.5 K and 300 K. By using this set-up, S and р of single crystalline YbMn_2Ge_2 and EuCo_2P_2 under high pressure were measured with enough accuracy. The temperature dependences of S and р show drastic changes at the critical pressure P_c in both compounds. The measurement results indicate that the simultaneous measurement of S and р is a usuful tool to study the pressure-induced phase transitions. 続きを見る
5.

論文(リポジトリ)

論文(リポジトリ)
高江洲, 義尚 ; 仲間, 隆男 ; 辺土, 正人 ; 内間, 清晴 ; 矢ヶ崎, 克馬 ; A. T. Burkov ; Takaesu, Yoshinao ; Nakama, Takao ; Hedo, Masato ; Uchima, Kiyoharu ; Yagasaki, Katsuma
出版情報: 琉球大学理学部紀要 = Bulletin of the College of Science. University of the Ryukyus.  pp.1-6,  2011-09.  琉球大学理学部
URL: http://hdl.handle.net/20.500.12000/22107
概要: Electrical resistivity p and thermopower S of Y_<1-x>R_xCo_2 (R=Gd, Tb, Dy, Ho and Er) Laves phase systems were measured at temperatures from 1.5 K to 300 K in magnetic fields up to 15 T and under hydrostatic pressures up to 2 GPa. The universal linear relation between the pressure and magnetic field derivatives of the resistivity, dp/dP vs. dp/dB, was observed in the Y_<1-x>R_xCo_2 systems. Similar scaling behavior was found for the thermopower dependence on pressure and magnetic field. 続きを見る
6.

論文(リポジトリ)

論文(リポジトリ)
Uchima, Kiyoharu ; Nakama, Takao ; Yagasaki, Katsuma
出版情報: 琉球大学理学部紀要 = Bulletin of the College of Science. University of the Ryukyus.  pp.11-29,  2006-03.  琉球大学理学部
URL: http://hdl.handle.net/20.500.12000/9167
7.

論文(リポジトリ)

論文(リポジトリ)
高江洲, 義尚 ; 仲間, 隆男 ; 矢ケ崎, 克馬 ; Burkov, A.T ; Takaesu, Yoshinao ; Nakama, Takao ; Yagasaki, Katsuma
出版情報: 琉球大学理学部紀要 = Bulletin of the College of Science. University of the Ryukyus.  pp.1-10,  2006-03.  琉球大学理学部
URL: http://hdl.handle.net/20.500.12000/9187
概要: Electrical resistivity of Y_<1-x>Gd_xCo_2 system has been measured at temperatures from 2 K to 300 K in magnetic fields up to 15 T and under pressure up to 10 GPa. The electrical resistivity of the compounds with the composition of x < 0.3 show anomalous dependences of composition and magnetic field at low temperatures. The pressure effect on electrical resistivity of Y_<1-x>Gd_Co_2 at low temperatures is in good agreement with the variation of magnetoresistance. The anomalous behavior can be explained by an interplay of metamagnetic instability of Co 3d electrons and structural disorder within rare earth sublattice. 続きを見る
8.

論文(リポジトリ)

論文(リポジトリ)
矢ケ崎, 克馬 ; 二木, 治雄 ; 仲間, 隆男 ; Yagasaki, Katsuma ; Niki, Haruo ; Nakama, Takao
出版情報: 1999-02.  矢ケ崎克馬
URL: http://hdl.handle.net/20.500.12000/9448
概要: 平成9-10年度文部省科学研究費補助金(基盤研究(C)(2))研究成果報告書<br />研究概要 : 1. 圧力効果の実験は3Kから室温までの温度範囲で電気抵抗、帯磁率を測定することに.よって行った(1)1GPaまでの圧力範囲で は、ゼロ磁場中ではクランプ式マイクロボンベを用い、5Tまでの磁場中ではスウェンソン式圧力装置を用いた。(2)1GPaか8GPaまではキュ-ビックアンピルを用いた。2. (1)CeRu_2の超伝導転移点は0.5GPaまでは圧力が増加すると共にほぼ直線的に減少し、それ以上の圧力では圧力と共に直線的に増加した。この原因は未解明である。(2)電気抵抗は低温で温度の二乗に比例しているが、その係数の圧力依存はちょうど超伝導移点の場合の逆の依存をした。(3)上記の結果から転移点の圧カ依存は単純なBCS理論では説明できない。3. CeRu_2ついてトンネル電子分光を行ったところ、強結合のBCS超伝導であることが明瞭となった。4. (1)5.5GPaでceRu_2は圧力に誘起された結晶変態を約9OKにて行う。この結晶変態には温度履歴も圧カ履歴も見られなかった。(2)結晶変態点は1GPaあたり約60Kの割合で増加する。(3)高圧下のX線測定の結果変態前後で圧縮率はほぼ同じであることが判明したが、変態後の結晶構造は未解明である。5. Ce_<0.97>La_<0.03>Ru_2の超伝導転移点は0.5GPaまでの圧力範囲、5Tまでの磁場中では全てCeRu_2とほぼ同じ割合で圧力増加と共に減少した。6. Ce_<0.8>La_<0.2>Ru_2の超伝導転移点は8GPaまでの圧カ範囲で圧カ増加と共に増加した。また電気抵抗から推察される状態密度も非常に小さい。7. LaRu_2.の超伝導転移点は8GPaまでの圧力範囲で圧力増加と共に減少した。8. Ce_<1-x>La_xRu_2の熱電能を測定した結果、組成の中間領域では状態密度が減少し、フェルミ面の形状はx=0.5を境界として急激に変化していることが判明した。9. 今後フェルミ面の詳細と超伝導の関連を解明することが重要である。<br />1) The tunnel electron spectrography revealed that the superconducting property of CeRu_2 is strongly coupled BCS type. 2) The superconducting transition temperature T0 of CeRu_2 decreases with pressure up to 0.5 Gpa but increases above it until the pressure goes up to 5.5GPa where the pressure induced phase transition occurs. In the induced phase, T_c decreases sharply. 3) X ray measurements were performed under high pressure and revealed the transition is structural one, however the structure type cannot be confirmed yet. 4) The resistivity of CeRu_2 depends on T^2 at low temperature. The density of state at Fermi level deduced from the coefficients of T^2 dependence has just opposite pressure dependence as T_c. 5) Pressure dependence of T_c and DOS of LaRu^2 decrease with increasing pressure up to 8GPa. 6) LaRu2 and Ce_<0.8>La_<0.2>Ru_2 do not have a pressure induced phase transition up to 8GPa. 7) DOS at the Fermi level of Ce_<1-X>La_XRu_2 deduced from the resistivity shows a deep minimum around x= 0.2 just like as composition dependence of T_c. 8) The thermopower was measured on Ce_<1-X>La_XRu_2. I t appeared that the shape of the Fermi level is divided into tow groups around x = 0.5.<br />未公開:P.9以降(論文別刷のため) 続きを見る
9.

論文(リポジトリ)

論文(リポジトリ)
仲間, 隆男 ; 辺土, 正人 ; 玉城, 純孝 ; Resel, R. ; Burkov, A.T. ; 矢ヶ崎克馬 ; Nakama, Takao ; Hedo, Masato ; Tamashiro, Junko ; Resel, Roland ; Burkov, Alexander T. ; Yagasaki, Katusma
出版情報: 琉球大学理学部紀要 = Bulletin of the College of Science. University of the Ryukyus.  pp.21-38,  1998-09.  琉球大学理学部
URL: http://hdl.handle.net/20.500.12000/9287
概要: We describe the system for thermopower measurement in magnetic fields up to 17 T in the temperature range from 3 K to 300 K. A special heating technique named "Seesaw heating method", a method similar to ac method, was developed and resulted in good thermal stability and high accuracy. Finding an empirical formula for all the calibration curves of chromel wire utilized as reference material enables us to measure thermopower at any field and at any temperature. The experimental results on GdAl_2 have been successfully analyzed on the basis of Mott's 2-band model with polalized conduction bands using linearized Boltzmann equation. 続きを見る
10.

論文(リポジトリ)

論文(リポジトリ)
仲間, 隆男 ; 大吉, 隆文 ; 辺士, 正人 ; 玉城, 純孝 ; 内間, 清晴 ; Burkov, A.T. ; 矢ヶ崎, 克馬 ; Nakama, Takao ; Oyoshi, Takafumi ; Hedo, Masato ; Tamashiro, Junko ; Uchima, Kiyoharu ; Burkov, Alxander T. ; Yagasaki, Katsuma
出版情報: 琉球大学理学部紀要 = Bulletin of the College of Science. University of the Ryukyus.  pp.11-20,  1998-09.  琉球大学理学部
URL: http://hdl.handle.net/20.500.12000/9288
概要: The experimental set-up for simultaneous measurements of electrical resistivity and thermopower in the temperature range between room temperature and 1300 K was developed. The mechanical contacts of thermocouples, current leads and potential probes with sample were Utilized make it possible to measure a large variety of materials and result in a flexibility with respect to the sample form and dimension. The resistivity and thermopower of pure Ni, CeB_6 heavy fermion compound and a Cr-Si thin film composite are presented as test material to demonstrate the possibilities and accuracy of our experimental set-up. 続きを見る