| Project/Area Number |
18540337
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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 | University of Tsukuba |
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Principal Investigator |
MORISHITA Masashi University of Tsukuba, Graduate School of Pure and Applied Sciences, Associate Professor (90251032)
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| Co-Investigator(Kenkyū-buntansha) |
TAKAGI Takeo Fukui University, Faculty of Technology, Associate Professor (00206723)
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| Project Period (FY) |
2006 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥3,920,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥420,000)
Fiscal Year 2007: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000)
Fiscal Year 2006: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Keywords | Two-Dimensional / Quantum Spin / Geometrical Frustration / Helium-3 / Graphite / Multiple Spin Exchange / Triangular Lattice / Kagome Lattice / ヘリウム3 / フラストレーション / 磁場 / 熱伝導 / スピン波 |
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| Research Abstract |
Helium-3 solid film adsorbed on a graphite substrate is widely accepted to be almost ideal two-dimensional quantum spin system. On the other hand, it possesses extraordinary strong frustration. In this research, heat capacities and thermal conductivities of helium-3 solid films have been measured in zero or weak magnetic fields, and some following new information has been revealed.
1) Heat capacity of helium-3 films is strongly affected even by weak magnetic field, which is weaker than the exchange interaction more than one decade. In the antiferromagnetic film, spin gap seems to be introduced by the magnetic field. In the ferromagnetic films, short range spin ordering is suppressed by the magnetic filed. These anomalous behaviors might arise from strong frustration.
2) Between helium-3 films and graphite substrates, heat is transferred only by local spots, which should be impurities in graphite substrates. Within the helium-3 films, heat is transferred by phonons and spin excitations. This information is valuable not only in cryogenics application. The measured thermal conductance gives information about the temperature variation of the spin correlation length.
3) The adsorption structure of the second layer 4/7 phase, which has recently been proposed, gives a possibility of a realization of S=1/2 quantum spins on kagome lattice by replacing a quarter of second layer helium-3 with helium-4 in the 4/7 phase. Heat capacity measurements of such helium 3 - helium 4 mixture film strongly suggest the realization of kagome lattice. They also agree with theoretical predictions that growth of short range spin ordering on kagome lattice is slower than on triangular lattice.
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