Fermi Surface and Magnetic Properties in Ferromagnet CoS2 and Paramagnet CoSe2 with the Pyrite-type Cubic Structure

International Conference on Strongly Correlated Electron Systems 2016

Teruya, A.^1 ; Suzuki, F.^1 ; Aoki, D.^2 ; Honda, F.^2 ; Nakamura, A.^2 ; Nakashima, M.^3 ; Amako, Y.^3 ; Harima, H.^4 ; Uchima, K.^5 ; Hedo, M.^6 ; Nakama, T.^6 ; Onuki, Y.^6

Graduate School of Engineering and Science, University of the Ryukyus, Nishihara, Okinawa

903-0213, Japan^1

Institute for Materials Research, Tohoku University, Oarai, Ibaraki

311-1313, Japan^2

Faculty of Science, Shinshu University, Nagano, Matsumoto

390-8621, Japan^3

Graduate School of Science, Kobe University, Kobe

657-8501, Japan^4

General Education, Okinawa Christian Junior College, Nishihara, Okinawa

903-0207, Japan^5

Faculty of Science, University of the Ryukyus, Nishihara, Okinawa

903-0213, Japan^6

关键词: Cyclotron-effective mass;    De Haas-van Alphen (dHvA) effect;    Electronic specific heat coefficient;    Energy band calculation;    Ferromagnetic state;    Four-fold symmetry;    High quality single crystals;    Temperature dependence;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/807/1/012001/pdf
DOI  :  10.1088/1742-6596/807/1/012001

来源: IOP

【 摘 要 】

We succeeded in growing high-quality single crystals of pyrite-type cubic compounds CoSe2and CoS2using a transport agent of CoBr2and measured the electrical resistivity, specific heat, magnetic susceptibility, magnetization, and the 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 TC= 122 K and an ordered moment μs= 0.93 μB/Co. The γ value of 21 mJ/(K2•mol) in CoS2is slightly larger than that of CoSe2. A large ordered moment, together with a large γ value, is a characteristic feature in 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 13m0in the dHvA experiments. The detected dHvA branches in CoS2and CoSe2are discussed on the basis of the results of energy band calculations, revealing a broken four-fold-symmetry in the angular dependence of the dHvA frequency.