1996 Fiscal Year Final Research Report Summary
Thermal Study of Reentrant Metal-Insulator Transition of DCNQI-Cu System
| Project/Area Number |
07454087
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 | Toho University |
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Principal Investigator |
NISHIO Yutaka Toho University, Department of Physics, Associate Professor, 理学部, 助教授 (20172629)
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| Co-Investigator(Kenkyū-buntansha) |
TAMURA Masafumi Toho University, Department of Physics, Lecturer, 理学部, 講師 (00231423)
KAJITA Koji Toho University, Department of Physics, Professor, 理学部, 教授 (50011739)
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| Project Period (FY) |
1995 – 1996
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| Keywords | Specific Heat / Latent Heat / CDW / AntiferroMagnetism / M-I Transition / Phase Transition / Deuteration / Methyl Rotation |
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| Research Abstract |
Under hydrostatic pressure of effective pressure introduced by deuteration of DCNQI molecules, (DMe-DCNQI)_2Cu system exhibits the reentrant metal-insulator transition (metal-insulator-metal) accompanied by three fold lattice distortion. In this system, not only electrical properties but also magnetic properties drastically change across the transition. We have been studying the specific heat and latent heat on samples, in which "chemical pressure" can be precisely controlled by using selectively deuterated (DMe-DCNQI)_2Cu in the temperature region (0.5K<T<100K) using the thermal, pulse and DTA methods.
We have succeeded in precisely determining temperature dependence of entropy of the metallic and insulator states by the these experimental results in the vicinity of the higher temperature and lower temperature M-I transitions. In the insulator phase, electrons are localized and there is no gammaT contribution to the specific heat and entropy. On the other hand, there appears the freedom of Cu^<2+> spin. This spin system undergoes the antiferromagnetic phase transition at 6.8K.The entropy due to the spin system obtained by integrating the specific heat. It grows in the temperature range of 2-20K.Above 20K the spin system becomes completely random and entropy due to this freedom take a constant value. The entropy of the spin system in the insulator phase and the latent heat at the transition gives the information of the entropy of electron system in the metallic phase. We can calculate the free-energy of the electronic system in both phases and reconstruct the mysterious and complicated phase diagram of DMe-Cu system. We clarified that the competition between these gammaT contribution in metallic phase and freedom of Cu^<2+> spins in insulator phase drives the reentrant M-I transition.
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