| Project/Area Number |
16540300
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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 |
Condensed matter physics II
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| Research Institution | Hokkaido University |
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Principal Investigator |
YAMAMOTO Shoji Hokkaido University, Faculty of Science, Professor (90252551)
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| Project Period (FY) |
2004 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥3,190,000 (Direct Cost: ¥3,100,000、Indirect Cost: ¥90,000)
Fiscal Year 2007: ¥390,000 (Direct Cost: ¥300,000、Indirect Cost: ¥90,000)
Fiscal Year 2006: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2005: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2004: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Keywords | ferrimagnets / nanomagnets / NMR / modified spin-wave theory / multimagnon scattering / numerical diagonalization / dynamic susceptibility |
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| Research Abstract |
A modified spin-wave theory is developed and applied to low-dimensional quantum magnets. Double-peaked specific heat for one-dimensional ferrimagnets, nuclear spin-lattice relaxation in ferrimagnetic chains and clusters, and thermal behavior of Haldane-gap antiferromagnets are described within the scheme. Mentioning other bosonic and fermionic representations as well, we demonstrate that spin waves are still effective in low dimensions.
Mesoscopic magnetism is one of the hot topics in materials science, where we can observe a quantum-to-classical crossover on the way from molecular to bulk magnets. Metal-ion magnetic clusters are thus interesting and among others is a series of molecular rings, which allows us to systematically investigate zero-dimensional spin dynamics as a function of the molecule size and the spin magnitude. The nuclear spin-lattice relaxation time Ti works as a powerful probe to the low-frequency spin dynamics and has indeed been measured for various metallic wheels containing copper, chromium, and iron ions. Thus motivated, we microscopically calculate 1/ Ti for both ferromagnetic and antiferromagnetic ring clusters, taking account of crystal-field anisotropies and anisotropic spin-spin interactions as well as the Heisenberg interaction. The following figure compares our calculations with experiments] on the ferromagnetic ring cluster Cu6, where we stress the lifetime broadening of descrete energy levels in proportion to Ti and the nonnegligible anisotropy effect as the key factors to interpret the characteristic peaks of 1/ Ti as a function of T. We calculate the antiferromagnetic ring cluster Cu8 as well and point out possible significance of the Dzyaloshinsky-Moriya interaction.
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