| Project/Area Number |
06640461
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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 Shoichi Muroran Institute of Technology Professor, 工学部, 教授 (80155936)
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| Co-Investigator(Kenkyū-buntansha) |
EBISU Shuji Muroran Institute of Technology Research Associate, 工学部, 助手 (10250523)
SHIROTANI Ichimin Muroran Institute of Technology Professor, 工学部, 教授 (90110692)
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| Project Period (FY) |
1994 – 1996
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| Project Status |
Completed (Fiscal Year 1996)
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| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1996: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1995: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1994: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Keywords | Spinel-type Compounds / CuIr_2S_4 / CuIr_2Se_4 / Metal-Insulator Transition / ^<193>Ir Mossbauer effect / Mixed Valence / Charge Ordering / Jahn-Teller Effect / メスバウァー効果 / 核磁気共鳴 / 構造相転移 |
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| Research Abstract |
The oxyspinels have been extensively studied mainly for the magnetic properties. In contrast to the oxyspinels sulphospinels exhibit the wide variety of physical properties. We have synthesized successfully a new spinel-type compound CuIr_2S_4 and discovered a metal-insulator (M-I) transition. After this discovery of M-I transition, many researchers are stronglyinterested in this new compounds all over the world. This new thiospinel CuIr_2S_4 exhibits a metal-insulator transition at 226K.This metal-insulator transition is associated with astructural phase transition from a cubic to a tetragonal structure with decreasing temperature. The high-temperature metallic phase of CuIr_2S_4 reveals Pauli paramagnetism and the lower-temperature insulating phase has semiconductive behavior with a rather large diamagnetic contribution due to the core electrons. A sharp heat capacity anomaly is observed. The enthalpy and entropy of the transition are found to be 3.50kJmol^<-1> and 15.6JK^<-1> mol^<-
… More
1>, respectively. The electrical resistivity in CuIr_2S_4 shows activated conduction with an activation energy of 4.7*10^2 eV between 140 and 200K.The magnetic susceptibility exhibits a sharp change near 228K.There has been a lot of investigation for the M-I transition in CuIr_2S_4. However, the origin and the driving force for the structural phase transition and the M-I transition is not understood at the present time. The Jahn-Teller effect can not explain these behavior, but the situation is rather complicated. The mechanism of the M-I transition in CuIr_2S_4 remains enigmatic, which must be solved. It is well known that magnetite Fe_3O_4 undergoes a phase transition (the Verwey transition) accompanied by a sudden change of conductivity at 119K.A possibility and the analogy for the mechanism in the M-I transition has been pointed out. Further detailed study to clarify the novel phenomena is currently under way. It is our hope that the systematic measurements presented below for the system of CuIr_2 (S_<1-x>, Se_x)_4 will be helpful and lead to the fruitful discussion. Less
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