| Project/Area Number |
06044031
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| Research Category |
Grant-in-Aid for international Scientific Research
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| Allocation Type | Single-year Grants |
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| Section | Joint Research |
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| Research Institution | University of Tokyo (1995)
University of Tsukuba (1994) |
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Principal Investigator |
TAKAYAMA Hajime Institute for Solid State Physics, University of Tokyo Professor, 物性研究所, 教授 (40091475)
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| Co-Investigator(Kenkyū-buntansha) |
ORBACH R. University of California, Riverside, 教授
CLARK W.G. University of California, Los Angeles, 教授
CAMPBELL I. Physique des Solides, Universite Paris-Sud, 教授
OCIO M. Service de Physique de l'Etat Condense, Commissariat a l'Energie Atomique Saclay, 凝縮系物理部門, 磁性研究室長
KAWAMURA Hikaru Faculty of Engineering and Design, Kyoto Institute of Technology, 工芸学部, 教授 (30153018)
ITO Atsuko Faculty of Science, Ochanomizu University, 理学部, 教授 (20017180)
MIYAKO Yoshihito Faculty of Science, Osaka University, 理学部, 教授 (10000837)
SUZUKI Masuo Faculty of Science, University of Tokyo, 理学系研究科, 教授 (80013473)
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| Project Period (FY) |
1994 – 1995
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| Keywords | Complex systems / Frustrated systems / Spin glasses / Ceramic Superconductors / Heavy electron / Spin-density wave / Aging phenomena / Slow dynamics / Reentrant transition |
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| Research Abstract |
In the course of the project several members and their collaborators were individually exchanged between the two countries (France and US) and Japan. The two workshops were held ; one on October 17-18,1994 at University of Tsukuba, and the other entitled "Physics of Frustrated Systems" on December 4-6,1995 at CEA-Saclay. Below we briefly describe the main results obtained by the project.
1) Transitions and Dynamics in spin glasses (SG's) : By the computational method Takayama has shown that slow dynamics in the 'Griffiths phase' consists of two processes, ordinary critical dynamics and cluster dynamics, while Campbell has pointed out a non-universal nature of Ising SG's. Ito has observed a divergent bahavior in the nonlinear susceptibility at the reentrant transition point to the mixed phase.
2) Aging Phenomena in SG's in Magnetic Fields : Ocio has found a universal scaling form for the time development of TRM and IRM including their waiting time dependence, while Orbach has proposed a way to extract the overlap function P (q) from the observed aging phenomena.
3) Phase Dynamics in Granular (Ceramic) Superconductors : From the measurement on 1/f noise Ocio has pointed out a possible existence of pi-junction, and Kawamura has developed a theory of the random freezing of 'chiralities' in these systems.
4) Heavy Electron Systems Ce (Ru_<0.85>Rh_<0.15>)_2Si_2 : In this material Miyako has observed the crossover from the high-T localized spin state to the low-T heavy electron state, and then to the spin-density wave (SDW) phase associated with the INVAR effect.
5) SDW Dynamics in (TMTSF)_2PF_6 : Clark has found that the repining process of SDW is governed by thermally excited quasi-particles at high T,but by their quantum tunneling at low T.
6) General Theory for Phase Transitions : Suzuki has developed general theories, such as the 'decomposition of exponential operators', and has applied them to various systems with exotic phase transitions.
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