| Project/Area Number |
15540378
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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 |
Mathematical physics/Fundamental condensed matter physics
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| Research Institution | Ariake National College of Technology |
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Principal Investigator |
MURAOKA Yoshinori Ariake National College of Technology, Common Technical Courses, Associate Professor, 共通専門, 助教授 (60229953)
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| Co-Investigator(Kenkyū-buntansha) |
NISHIYAMA Harutoshi Ariake National College of Technology, Department of General, Associate Professor, 一般教育科, 助教授 (00280488)
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| Project Period (FY) |
2003 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2004: ¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 2003: ¥2,000,000 (Direct Cost: ¥2,000,000)
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| Keywords | Competing spin system / ANNNI model / A3NNI model / Higher order spin interaction / Thin film / Monte Carlo simulation / Partially disordered state / Non-equilibrium relaxation method / 臨界指数 / A3NNI model / モンテカルロシミュレーション / フーリエ係数 |
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| Research Abstract |
The ANNNI and A3NNI models are familiar as the spin systems with the competition between interactions with different range (for example, 1st, 2nd, and 3rd nearest-neighbors). In this study, we consider the S=1 ANNNI and A3NNI models with the higher order spin interaction. Using the analytical methods and the Monte Carlo simulation (MC), we investigate the role and importance of the higher order spin interaction and the spin quantum number in the competing spin systems, theoretically.
1) The extended A3NNI model
We propose the extended A3NNI model with the higher order spin interaction as model explaining the phase transition from the k=1/3 modulated structure to the antiferromagnetic structure in UNi2Si2. The temperature dependence of the Fourier coefficients in the Modulated structures are calculated by MC, and we show the appearance of this phase transition.
2) The extended ANNNI model on the thin film
Using MC, the magnetic phase diagram of S=1 ANNNI model with the 3-site 4-spin interaction is obtained, and the finite-size scaling shows that 4 phase transition lines are the second order phase transition. These results suggest the existence of the tetracritical point.
3) The extended ANNNI model with alternating intralayer interactions
Using MC with non-equilibrium relaxation method and the finite-size scaling, we calculated critical temperatures and critical exponents. The obtained exponents show that the ordinary universality does not hold in this model, and suggests that the weak universality holds.
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