| Project/Area Number |
14340097
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体物性Ⅱ(磁性・金属・低温)
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| Research Institution | Tohoku University |
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Principal Investigator |
KOIKE Yoji Tohoku University, Graduate School of Engineering, Professor, 大学院・工学研究科, 教授 (70134038)
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| Co-Investigator(Kenkyū-buntansha) |
KATO Masatsune Tohoku University, Graduate School of Engineering, Associate Professor, 大学院・工学研究科, 助教授 (50211850)
NOJI Takashi Tohoku University, Graduate School of Engineering, Research Associate, 大学院・工学研究科, 助手 (50180740)
ADACHI Tadashi Tohoku University, Graduate School of Engineering, Research Associate, 大学院・工学研究科, 助手 (40333843)
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| Project Period (FY) |
2002 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥17,000,000 (Direct Cost: ¥17,000,000)
Fiscal Year 2004: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 2003: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 2002: ¥13,800,000 (Direct Cost: ¥13,800,000)
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| Keywords | quantum spin system / low-dimensional system / thermal conductivity / magnon / spin gap / antiferromagnetism / spin flop transition / Bose-Einstein condensation / 高温超伝導 / 磁場誘起磁気秩序 / ストライプ秩序 / 銅酸化物 / 強磁性 |
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| Research Abstract |
We have studied the thermal conductivity and other physical properties of several copper oxides regarded as low-dimensional quantum spin systems, in order to clarify the mechanism of the giant thermal conductivity due to magnons and also to clarify whether the thermal conductivity measurement is powerful for the detection of a phase transition or not.
We have discovered large thermal conductivity due to magnons in the four-leg spin-ladder system La_2Cu_2O_5 and the two-dimensional spin system Cu_3B_2O_6.
In one-dimensional spin systems Sr_2CuO_3 and SrCuO_2, we have proved from the study of the impurity effects that the thermal conductivity due to magnons is very large and that the thermal conduction is ballistic as theoretically expected.
From these results, it has been concluded that both the large antiferromagnetic interaction between spins and the large dispersion of magnons give rise to the large thermal conductivity due to magnons.
Moreover, marked changes of the thermal conductivity have been observed at the following phase transitions; the spin-flop transition in the antiferromagnetically ordered state of Ca_2Y_2Cu_5O_<10> and Cu_3B_2O_6, the Bose-Einstein condensation transition off magnons in TlCuCl_3 under high magnetic fields at low temperatures, and the field-induced magnetic order in La_<2-x>Sr_xCUO_4 and La_<2-x>Ba_xCuO_4. Accordingly, we have concluded that the thermal conductivity measurement is a powerful probe to detect and study a phase transition.
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