Magnetic Phase Diagram of the Heavy Fermion Superconductor PrOs_4Sb_<12>

概要

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We investigated the magnetic phase diagram of the first Pr-based heavy fermion superconductor PrOs_4Sb_<12> by means of high-resolution dc magnetization measurements in low temperatures down to 0.06 K. The temperature dependence of the magnetization M(T) at 0.1 kOe exhibits two distinct anomalies at T_<c1> = 1.83 K and T_<c2> = 1.65 K, in agreement with the specific heat measurements at zero field. Increasing magnetic field H, both T_<c1> (H) and T_<c2> (H) move toward lower temperatures without showing a tendency of intersecting to each other. Above 10 kOe, the transition at T_<c2> (H) appears to merge into a line of the peak effect which is observed near the upper critical field H_<c2> in the isothermal M(H) curves, suggesting a common origin for these two phenomena. The presence of the field-induced ordered phase (called phase A here) is confirmed for three principal directions above 40 kOe, with the anisotropic A-phase transition temperature TA: T^<|100|>_A >T^<|111|>_A > T^<|110|>_A. The present results are discussed on the basis of crystalline-electrical-field level schemes with a non-magnetic ground state, with emphasis on a Γ_1 singlet as the possible ground state of P_Γ^<3+> in PrOs_4Sb_<12>.
社団法人日本物理学会の論文
2003-06-15