| Budget Amount *help |
¥3,830,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥330,000)
Fiscal Year 2007: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
Fiscal Year 2006: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2005: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
The f electrons of cerium compounds exhibit a variety of characteristic features including spin and charge orderings, spin and valence fluctuations, heavy-fermions and anisoiropic superconductivity. In cerium compounds, the Rudemran-Kittel-Kasuya-Yosida (RKKY) interaction and the Kondo effect compete with each other. The RKKY interaction enhances the long-range magnetic order, while the Kondo effect quenches the magnetic moments of the localized f electrons. Most of the cerium compounds order antiferromagnetically with the Neel temperature T_N, because the RKKY interaction overcomes the Kondo effect at low temperatures.
Recently, a new aspect of cerium and uranium compounds with magnetic ordering has been discovered. When a pressure P is applied to compounds with antiferromagnetic ordering such as CeCu_2Ge_2, CeIn_3, and CePd_2Si_2, T_N reaches zero at the quantum critical pressure Pc, and superconductivity is observed at around P_c. The transition from the magnetically ordered state to the nonmagnetic state under pressure, crossing the quantum critical point, is the most interesting issue in strongly correlated f electron systems.
We have depeloped high pressure cells for the de Haas-van Alphen experiment and electrical resistivity measurement which can be rotated in the magnetic fields, and investigated the heavy fermion state including the pressure-induced superconductor, which are summarized as follows ;
1. Discovery of the pressure-induced superconductor CeIrSi_3 and CeCoGe_3 and huge upper critical field with strong coupling behavior
2. Split Fermi surface due to antisymmetric spin-orbit interaction based on the non-conetrosymmetric crystal structure in CeTX_3 (T : transition metal, X : Si, Ge).
3. Pressure-induced heavy-fermion superconductivity in Ce_2Ni_3Ge_5 and CePt_3Si,
4. Pressure phase diagram in a ferromagnet CePtAl and an antiferromagnet CeTl_3
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