著者

Teruya Atsushi Suzuki Fuminori Aoki Dai Honda Fuminori Nakamura Ai Nakashima Miho Amako Yasushi Harima Hisatomo Hedo Masato Nakama Takao Onuki Yoshichika

出版者

The Physical Society of Japan

雑誌

Journal of the Physical Society of Japan (ISSN:00319015)

巻号頁・発行日

vol.85, no.6, pp.64716-1-10, 2016-06-01

被引用文献数

11

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We succeeded in growing high-quality single crystals of the pyrite-type cubic compounds CoSe₂and CoS₂using the transport agent CoBr₂and measured the electrical resistivity, specific heat, magnetic susceptibility, magnetization, and de Haas–van Alphen (dHvA) effect. We confirmed that CoSe₂is an exchange-enhanced paramagnet revealing a broad maximum at around 50 K in the temperature dependence of the magnetic susceptibility. The electronic specific heat coefficient is moderately large, γ = 18 mJ/(K²·mol). On the other hand, CoS₂is a ferromagnet with a Curie temperature <italic>T</italic>_C= 122 K and an ordered moment μ_s= 0.93 μ_B/Co. The γ of 21 mJ/(K²·mol) of CoS₂is slightly larger than that of CoSe₂. A large ordered moment, together with a large γ, is characteristic of CoS₂because CoS₂is a half-metallic spin state in the ferromagnetic state. Correspondingly, we detected a main dHvA branch with a large cyclotron effective mass of 13<italic>m</italic>₀in the dHvA experiments. The detected dHvA branches in CoS₂and CoSe₂are discussed on the basis of the results of energy band calculations, revealing a broken fourfold symmetry in the angular dependence of the dHvA frequency.

著者

Teruya Atsushi Kakihana Masashi Takeuchi Tetsuya Aoki Dai Honda Fuminori Nakamura Ai Haga Yoshinori Matsubayashi Kazuyuki Uwatoko Yoshiya Harima Hisatomo Hedo Masato Nakama Takao Ōnuki Yoshichika

出版者

The Physical Society of Japan

雑誌

Journal of the Physical Society of Japan (ISSN:00319015)

巻号頁・発行日

vol.85, no.3, 2016-02-08

被引用文献数

9

著者

仲間 隆男 大吉 隆文 辺土 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

出版者

琉球大学理学部

雑誌

琉球大学理学部紀要 (ISSN:02869640)

巻号頁・発行日

no.66, pp.11-20, 1998-09

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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.

著者

Teruya Atsushi Suzuki Fuminori Aoki Dai Honda Fuminori Nakamura Ai Nakashima Miho Amako Yasushi Harima Hisatomo Hedo Masato Nakama Takao Onuki Yoshichika

出版者

The Physical Society of Japan

雑誌

Journal of the Physical Society of Japan (ISSN:00319015)

巻号頁・発行日

vol.85, no.6, pp.64716-1-10, 2016-06-01

被引用文献数

11

---

We succeeded in growing high-quality single crystals of the pyrite-type cubic compounds CoSe₂and CoS₂using the transport agent CoBr₂and measured the electrical resistivity, specific heat, magnetic susceptibility, magnetization, and de Haas–van Alphen (dHvA) effect. We confirmed that CoSe₂is an exchange-enhanced paramagnet revealing a broad maximum at around 50 K in the temperature dependence of the magnetic susceptibility. The electronic specific heat coefficient is moderately large, γ = 18 mJ/(K²·mol). On the other hand, CoS₂is a ferromagnet with a Curie temperature <italic>T</italic>_C= 122 K and an ordered moment μ_s= 0.93 μ_B/Co. The γ of 21 mJ/(K²·mol) of CoS₂is slightly larger than that of CoSe₂. A large ordered moment, together with a large γ, is characteristic of CoS₂because CoS₂is a half-metallic spin state in the ferromagnetic state. Correspondingly, we detected a main dHvA branch with a large cyclotron effective mass of 13<italic>m</italic>₀in the dHvA experiments. The detected dHvA branches in CoS₂and CoSe₂are discussed on the basis of the results of energy band calculations, revealing a broken fourfold symmetry in the angular dependence of the dHvA frequency.

著者

Nakamura Ai Uejo Taro Honda Fuminori Takeuchi Tetsuya Harima Hisatomo Yamamoto Etsuji Haga Yoshinori Matsubayashi Kazuyuki Uwatoko Yoshiya Hedo Masato Nakama Takao Ōnuki Yoshichika

出版者

The Physical Society of Japan

雑誌

Journal of the Physical Society of Japan (ISSN:00319015)

巻号頁・発行日

vol.84, no.12, 2015-11-26

被引用文献数

36

著者

Kakihana Masashi Teruya Atsushi Nishimura Kengo Nakamura Ai Takeuchi Tetsuya Haga Yoshinori Harima Hisatomo Hedo Masato Nakama Takao Ōnuki Yoshichika

出版者

The Physical Society of Japan

雑誌

Journal of the Physical Society of Japan (ISSN:00319015)

巻号頁・発行日

vol.84, no.9, pp.94711-1-8, 2015-08-21

被引用文献数

17

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We grew single crystals of ullmannite NiSbS and PbBiSe with the cubic chiral structure and carried out electrical resistivity, specific heat, and de Haas–van Alphen (dHvA) experiments to clarify their Fermi surface properties. The Fermi surfaces were found to split into two, reflecting the non-centrosymmetric crystal structure. The splitting energies between the two nearly spherical electron Fermi surfaces named α and α′ were determined as 220 K in NiSbS and 1050 K in PdBiSe for <italic>H</italic>|| [100] or [001]. This difference in splitting energies between the two compounds originates mainly from the fact that the spin–orbit interactions of Ni-3<italic>d</italic>, Sb-5<italic>p</italic>, and S-3<italic>p</italic>electrons in NiSbS are smaller in magnitude than those of Pd-4<italic>d</italic>, Bi-6<italic>p</italic>, and Se-4<italic>p</italic>electrons in PdBiSe, respectively.