| Project/Area Number |
11440118
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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 PHYSICS, ASSOCIATED PROFESSOR, 理学部, 助教授 (20172629)
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| Co-Investigator(Kenkyū-buntansha) |
KAJITA Koji TOHO UNIVERSITY PHYSICS, PROFESSOR, 理学部, 教授 (50011739)
田村 雅史 東邦大学, 理学部, 講師 (00231423)
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| Project Period (FY) |
1999 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥9,600,000 (Direct Cost: ¥9,600,000)
Fiscal Year 2001: ¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 2000: ¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 1999: ¥4,200,000 (Direct Cost: ¥4,200,000)
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| Keywords | Deuteration / Metal-Insulator Transition / Thermal property / Schottky Specific Heat / Organic Conductor / Tunneling Rotation / Lattice vibration / 有機導体 / 金属-絶縁体 / CDW / Mott転移 / 秩序-無秩序転移 / 有機伝導体 / 分子内振動 |
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| Research Abstract |
Metal complex salts (DMe-DCNQI)_2Cu exhibits a reentrant metal-insulator transition under delicate pressure. The mixing of DCNQIπ electron and Cu 3d electron located near Fermi level generates 3dFermi face and suppresses low dimensional instability. We carried out adeuteration of methyl group, a size of which can control the electronic dimensionality and tune the reentrant M-I transition.
We have experimentally studied the mechanism of reentrant metal-insulator-metal transition of DCNQI-Cu system using this deuterated system. Measurements of specific heat and latent heat were carried out by thermal relaxation (0.5<T<40K), adiabatic pulse (20<T<100K) and Differential Thermal Analysis (DTA) methods on samples under various chemical pressures. From the experimental results, we determined the Gibbs free energy difference between metallic and insulating phases and succeeded to draw the phase diagram that reproduces the experimental result quite well. We conclude that the free energy change of free electrons (metallic phase) to localized electrons with spin 1/2 (insulating phase) is essential to drive the anomalous phase transition in this system. Contribution of lattice system is also clarified.
In this deuterated system, we have discovered that an orientation freedom in a deuterated methyl group brings two kinds of anomalous specific heat todeuterated (DMe-DCNQI)_2Cu system. In system containing methyl groups with one deuterium atom (CH_2D), we found Schottky type of specific heat. In system with CHD_2, we observed peaks not of Schottky type. To find out an origin and mechanism of these anomalies, we carried out the thermal study of the mixed crystals composed ofCH_2D and CHD_2. We clarified the conformational ordering of CHD_2 molecular along c axis in the DCNQI-Cu system.
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