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第48回 原研・兵県大合同コロキウム

日時: 平成20年10月27日(月) 16:30〜
Date and time: 27th Oct. (Mon.) 16:30〜
場所: 原子力機構SPring-8 4階応接室
Place: JAEA SPring-8, seminar room 4F
Title: Low Temperature Specific Heat and Magnetocaloric Effect of the Field-induced Spin-Density-Wave State
講演者: 鴻池貴子 氏 (東大物性研)
Speaker: Dr. Takako Konoike (ISSP, University of Tokyo)
Abstract:

In some quasi-one dimensional organic conductors, it is well known that a field-induced spin-density-wave (FISDW) state is stabilized in a magnetic field because of the imperfect nesting of the Fermi surfaces (FS's) and Landau quantization of the electrons at the resulting FS pockets. Most features of the FISDW state are basically understood in terms of so-called "standard model". However, some qualitative disagreements with the model still remain in (TMTSF)2ClO4, which has a superlattice structure below 24 K due to the anion ordering. One of the most interesting features is the "tree-like" structure inside the FISDW subphases reported in the caloric measurements. In spite of considerable theoretical and experimental efforts, the existence of the tree-like structure is still controversial. In this study, we have measured the specific heat and magnetocaloric effect of (TMTSF)2ClO4 at very low temperature to clarify the tree-like structure and the detailed temperature - magnetic field phase diagram of this salt. We observed successive anomalies in both measurements corresponding to the cascade transitions of the FISDW subphases. However, we have no clear evidence of the tree-like structure inside the subphases within our resolution. In the phase diagram constructed from the detailed specific heat measurements, we find the reentrance to the metallic phase between the adjacent FISDW subphases. The reason of this reentrance behavior and the detailed feature of the phase diagram will be discussed and compared with the previous theoretical models.