| Project/Area Number |
13130202
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| Research Category |
Grant-in-Aid for Scientific Research on Priority Areas
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| Allocation Type | Single-year Grants |
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| Review Section |
Science and Engineering
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| Research Institution | TOKYO INSTITUTE OF TECHNOLOGY |
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Principal Investigator |
TANAKA Hidekazu Tokyo Institute of Technology, Department of Physics, Professor, 極低温物性研究センター, 教授 (80188325)
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| Co-Investigator(Kenkyū-buntansha) |
OSHIKAWA Masaki University of Tokyo, Institute for Solid State Physics, Professor, 物性研究所, 教授 (50262043)
ONO Toshio Tokyo Institute of Technology, Department of Physics, Research Associate, 大学院理工学研究科, 助手 (40332639)
HOSOKOSHI Yuko Osaka Prefectural University, College of Integrated Arts and Science, Associate Professor, 総合科学部, 助教授 (50290903)
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| Project Period (FY) |
2001 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥102,300,000 (Direct Cost: ¥102,300,000)
Fiscal Year 2004: ¥12,900,000 (Direct Cost: ¥12,900,000)
Fiscal Year 2003: ¥21,900,000 (Direct Cost: ¥21,900,000)
Fiscal Year 2002: ¥33,200,000 (Direct Cost: ¥33,200,000)
Fiscal Year 2001: ¥34,300,000 (Direct Cost: ¥34,300,000)
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| Keywords | Magnetism / Experiments for Solid State Physics / Low Temperature Physics / Statistical Mechanics / High Magnetic Field / Quantum Spin Systems / Field-Induced Magnetic Phenomena / Low Dimensional Magnets / スピンギャップ / マグノン / ボース・アインシュタイン凝縮 / ESR / 磁場誘起相転移 / 磁化プラトー / TlCuCl_3 / 有機物低次元磁性体 / F_2PNNNO / BIP-TENO |
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| Research Abstract |
Coupled S=1/2 spin dimer systems such as T1CuCl_3 and KCuCl_3 which we developed undergo novel quantum phase transitions high magnetic fields. These systems often have singlet ground states with excitation gaps. In high magnetic field, one of the triplets whose energy decreases with magnetic field plays an important role. The triplet can hop to neighboring site as a quasi-particle and interact due to the transverse and longitudinal components of the interdimer exchange interaction. The quasi-particle has characteristics of boson and is called magnon. Consequently, the system can be described as interaction boson system, where magnetic field corresponds to the chemical potential. The field-induced antiferromagnetic (AF) ordering occurs when the hopping of magnons is dominant. The ordering can be described as the Bose-Einstein condensation (BEC) of magnons. We have perform various measurements on the field-induced AF ordering in TlCuCl, including magnetization, specific heat, neutron sca
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ttering ultrasonic attenuation, heat-conductivity, thermal expansion measurements. Together with theoretical analysis, we verify that 1 field-induced AF ordering in TlCuCl, is the BEC of magnons. Examples include that experimental critical exponent (1152 for the phase boundary agrees with theoretical φ=3/2, and that theoretical calculation based on the magnon BEC reproduces almost perfectly experimental phase boundary. By means of magnetization and neutron scattering measurements, we observed that spin gap systems T1CuCl_3 and KCuCl_3 undergo phase transition to antiferromagnetic state in hydrostatic pressure. This is the first example the pressure-induced magnetic quantum phase transition from the gapped state to the antiferromagnetic state. We observed magnetization plateau at one-third of the saturation magnetization in Cs2_CuBr_4 that is described as triangular antiferromagnet This plateau is attributed to interplay between spin frustration and quantum fluctuation. We developed many molecular magnet Examples include S=1 and 1/2 mixed spin system BIPNNBNO, S=1 honeycomb lattice antiferromagnet F_2PNNNO, S=1 spin ladder system BIPTENO and S=1/2 alternating antiferromagnetic chain F_5PNN. In BIPTENO, we observed magnetization plateau at one-quarter of the saturation magnetization. This plateau is realized by breaking translational symmetry. We observed the magnetic properties characteristic of the Tomonaga-Luttinger liquid for one-dimensional fermion system. We developed the general theory for electron spin resonance for one-dimensional antiferromagnet. Less
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