2000 Fiscal Year Final Research Report Summary
Single Crystal Growth of Sulphospinel CuIr_2S_4 which exhibits the metal-insulator transition
| Project/Area Number |
11640329
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体物性Ⅱ(磁性・金属・低温)
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| Research Institution | Muroran Institute of Technology |
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Principal Investigator |
NAGATA Soichi Muroran Institute of Technology, Dept.of Materials Science and Engineering, Professor, 工学部, 教授 (80155936)
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| Co-Investigator(Kenkyū-buntansha) |
EBISU Shuji Muroran Institute of Technology, Dept.of Materials Science and Engineering, Research Associate, 工学部, 助手 (10250523)
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| Project Period (FY) |
1999 – 2000
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| Keywords | CuIr_2S_4 / Single crystal growth / Metal-insulator transition / Sulphospinel / 5d-electron / Crystal transformation / Magnetic susceptibility / Electrical resistivity |
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| Research Abstract |
The normal sulphospinel CuIr_2S_4 exhibits a temperature-induced metal-insulator (M-I) transition around 226 K with structural transformation, showing hysteresis on heating and cooling With decreasing temperature, a symmetry change occurs from cubic to tetragonal symmetry and a change from the Pauli paramagnetism in metallic behavior to diamagnetism due to the atomic core orbital. A gap in the electronic density of states opens below the M-I transition temperature. It has been verified that d-electrons of Ir atom on the octahedral B-sites have a significant role for the M-I transition.
Single crystals of a sulphospinel CuIr_2S_4 have been successfully grown from bismuth solution by a slow cooling method for the first time. The grown crystals have a maximum edge of about 1 mm in size and a mirror-like shining surface. Optimum growth conditions are fairly strict. The specific weight of starting materials for the crystal growth is found to be 0.30 g of CuIr_2S_4 and 10.0 g of Bi in order to obtain good quality crystals. The starting and finishing temperatures for the slow cooling step in the temperature control are 1000 and 500 ℃. The pertinent cooling rate is 〜2 ℃/h. Since the volume of bismuth itself expands in the transition from liquid phase to solid phase, a simple method of separation of the grown crystals from the liquid solution is proposed for avoiding the mechanical damages to the grown crystals. The single crystals have the normal-spinel structure of the lattice constant a =9.849 Å at room temperature. A step-like anomaly in the susceptibility of the single crystals, corresponding to the metal-insulator transition in the resistivity, occurs much sharply than in the powder specimen.
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[Publications] G.L.W.Hart, W.E.Pickett, E.Z.Kurmaev, D.Hartmann, M.Neumann, A.Moewes, D.L.Ederer, R.Endoh, K.Taniguchi, and S.Nagata: "Electronic Structure of Cu_<1-x>Ni_xRh_2S_4 and CuRh_2Se_4 : Band-structure Calculations, X-ray Photoemission, and Fluorescence Measurements"Phys.Rev.No.6. B61. 4230-4237 (2000)
Description
「研究成果報告書概要(欧文)」より
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