| Budget Amount *help |
¥5,900,000 (Direct Cost: ¥5,900,000)
Fiscal Year 1992: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1991: ¥4,800,000 (Direct Cost: ¥4,800,000)
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| Research Abstract |
The magnetic correlation in the heavy fermion superconductor, CeCu<@D22.02@>D2Si<@D22@>D2 and Th-doped Ce<@D21-x@>D2Th<@D2x@>D2Cu<@D22.2@>D2Si<@D22@>D2, has been investigated by Cu nuclear magnetic resonance (NMR) and nuclear quadrupoleresonance (NQR). For CeCu<@D22.02@>D2Si<@D22@>D2 with T<@D2c@>D2 = 0.72KJ, a "magnetic transition" has been found at around 0.8 K in applied fields up to 3.5T. Below the transition temperature, Cu NMR loses the intensity suddenly without any broadening and shift of the spectrum, and the spin-echo decay rate, 1/T<@D22@>D2, at H = 13.3kOe, increases with decreasing temperature, which is different from the behavior expected in a static magnetically ordered state. The "magnetic transition" just above T<@D2c@>D2 is quite unusual in a sense that the ordered state may not be in a completely static regime, but possesses some dynamic aspect. We have constructed a magnetic phase diagram in the field-temperature plane for CeCu<@D22.02@>D2Si<@D22@>D2. To ensure the magnetic instability in CeCu<@D22@>D2 we have investigated a magnetic and superconducting phase diagram of Th-doped Ce<@D21-x@>D2Th<@D2x@>D2Cu<@D22.2@>D2Si<@D22@>D2. Static magnetic ordering with T<@D2n@>D2 = 2.4K and 4.5K for x=0.08 and 0.12, respectively, is evidenced by a pronounced broadening of the <@D163@>D1Cu-NQR and -NMR spectra and a mean-field type of anomaly in the specific heat. In contrast, for the lightly Th-doped compounds with x (] SY.ltoreq.[) 0.064, there has been observed neither any signature of a broadening of the NQR and NMR spectra nor an anomaly of the specific heat, but a dramatic reduction of the NMR and NQR intensities below a temperature ranging from 0.9 K to 1.3 K upon increasing Th-content. It is emphasized that the unusual "magnetic transition" found in undoped and lightly Th-doped CeCu<@D22.2@>D2Si<@D22@>D2 should be distinguished from the static magnetic ordering in the heavily Th-doped systems.
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