| Project/Area Number |
14540362
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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 | AOYAMA GAKUIN UNIVERSITY |
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Principal Investigator |
KUBO Ken Aoyama Gakuin University, College of Science and Engineering, Professor, 理工学部, 教授 (30015862)
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| Co-Investigator(Kenkyū-buntansha) |
TOZUKA Keisuke Kyoto University, Institute for fundamental Physics, Associate Professor, 基礎物理学研究所, 助教授 (80291079)
MOMOI Tsutomu Tsukuba University, Institute of Physics, Assistant, 物理学系, 助手 (80292499)
MIYAHARA Shin Aoyama Gakuin University, College of Science and Engineering, Assistant, 理工学部, 助手 (90365015)
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| Project Period (FY) |
2002 – 2003
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| Project Status |
Completed (Fiscal Year 2003)
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| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 2003: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2002: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Keywords | multiple spin exchange / scalar chirality / duality relation / helium3 solid layer / ladder spin system / magnetization plateau / triangular lattice / frustration / 拡張ハバード模型 / ストライプ融解相転移 / 希薄磁性半導体 |
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| Research Abstract |
We have investigated the spin systems with multiple exchange interactions as well as related spin systems without multiple exchanges theoretically, and obtained following results.
1)The ground state phase diagram of the system on the triangular lattice with 2-, 3- and 4-spin exchanges were determined under external magnetic field by means of the molecular field approximations. As the result it turned out that the phase diagram is quite complex. There appear 6-sublattice as well as 12-sublattice structures with scalar and vector chiral order close to the 120 degree structure when the antiferromagnetic interactions are strong. There are also large scale spatial structures with 144 and 72 sublattices close to ferromagnetic phase. More studies are necessary to confirm the stability of these large structures.
2)Effects of the 5- and 6-spin exchanges on the system on the triangular lattice were studied by means of the molecular field theory. It turned out that the 5-spin exchanges have strong effect in stabilizing the ferromagnetic phase while 6-spin exchanges do not affect the ground state too much.
3)We proved that there exists a rigorous duality relation between spin orders and chirality orders in spin systems on the ladder lattice with 4-spin exchanges. As a result we could rigorously proved that some ladder spin systems have ground states with scalar chirality. This duality relation was extended to the systems of correlated electrons on the ladder.
4)We have investigated a 1D spin system which cnsists of tetrahedral clusters theoretically and have shown that it will show a peculiar magnetization process with magnetization plateaus.
5)We investigated the effect of spin lattice interactions on magnetic plateaus in a 2D frustrated spin system SrCu_2(BO_3)_2. We proposed a spin-lattice model which can describe the magnetic plateaus experimentally observed.
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