Single Uranium-Site Properties of the Dilute Heavy Electron System U_xTh_<1-x>Ru_2Si_2 (x≤0.07)

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Specific heat C, electrical resistivity , magnetization M and magnetic susceptibilityχ have been measured for the dilute tetragonal heavy-electron compounds U_xTh_<1-x>Ru_2Si_2 (x≤0.07), in the temperature range 100 mK≤T≤360 K and in the magnetic fields H up to 55 kOe. Non-Fermi-liquid behavior with unusual ln T dependence of C, p andχ has been observed at the low temperatures : as the temperature is lowered below about 10 K, C/ T andχ increase logarithmically, and p decreases logarithmically. Systematical variations of these quantities with uranium concentration indicate that the observed non-Fermi-liquid behavior is ascribed to the properties of a single U ion embedded in the Th site of the ThRu_2Si_2 metal. The magnetization curves M vs H/T indicate a strong uniaxial magnetic anisotropy along the tetragonal c-axis as well as a strong reduction of the 5 f moment of U ions. A possible interpretation based on the recent developments of the S= 1/2 two-channel Kondo model is given.
社団法人日本物理学会の論文
1994-02-15