| Project/Area Number |
07640499
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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 |
物性一般(含基礎論)
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| Research Institution | Tohoku University |
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Principal Investigator |
MATSUBARA Fumitaka Tohoku University, Engineering, Professor, 工学部, 教授 (90124627)
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| Co-Investigator(Kenkyū-buntansha) |
SHIRAKURA Takayuki Iwate University, Humanity and Social Science, Associate Professor, 人文社会学部, 助教授 (90187534)
NAKAMURA Tohta Tohoku University, Engineering, Research Assistant, 工学部, 助手 (50280871)
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| Project Period (FY) |
1995 – 1996
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| Project Status |
Completed (Fiscal Year 1996)
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| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1996: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1995: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Keywords | Spin-Glass / Dilute Magnetic Alloys / Monte-Carlo Simulation / RKKY Model / Site-Random / Dipole Interaction / 希薄磁性金属 / クラスター熱浴法 / リエントラント相転移 |
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| Research Abstract |
1. Development of computer simulation algorithm
We have newly developed two simulation methods which are efficient for studying complex systems, especially for spin-glass models : (1) a hybrid Monte-Carlo spin-dynamics (HMCSD) method for the Heisenberg models, and (2) a cluster heat bath (CHB) method for the Ising models.
2. Simulation of the Rudermann-Kittel-Kasuya-Yoshida (RKKY) model
Metallic spin-glass alloys are described by using the RKKY model. (1) We have made detailed simulation of the RKKY model and determined the phase diagram of it.(2)We have studied effects of the dipolar interaction on the RKKY model just above its critical consentration and found that, as the temperature is decreased, the magnetization once increases below the Curie temperature then decreases as the temperature is further decreased. We believe this is a key point for reentrant spin-glass phenomena.
3. Mixtures of ferromagnetic and antiferromagnetic atoms
Mixtures of two magnetic atoms are another kind of complex systems for which a spin-glass is expected to occur. We have made computer simulations of both the Ising and Heisenberg models and obtained the following results. (1) In the Ising model, we have found an evidence of the occurrence of the spin-glass phase even for two-dimensions, in contrast with a previous speculation. (2) In the Heisenberg model, we have found a novel magnetic phase in which a longitudinal ferromagnetism and a transverse antiferromagnetism coexist.
4. Other frustrated models
We have also investigated magnetic structures of various models with some frustrations. Those are a quantum spin systems on the triangular lattice, Ising-like models with competing intaractions, and a ferromagnetic Heisenberg model with dipolar interactions.
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