Unusual nature of electronic and magnetic states of Sm1.85Ce0.15CuO4-delta

Abstract

Temperature-dependent magnetization (M(T)) and specific heat (C-p(T)) measurements were carried out on single-crystal Sm1.85Ce0.15CuO4-delta (T-c=16.5K). The magnetic anisotropy in the static susceptibility, chi equivalent to M/H, is apparent not only in its magnitude but also in its temperature dependence, with chi (perpendicular to) for H perpendicular to c larger than chi (parallel to) for H parallel to c, For both field orientations, chi does not follow the Curie-Weiss behavior due to the small energy gap of the J = 7/2 multiplet above the J = 5/2 ground-state multiplet. However, with increasing temperature, chi (parallel to)(T) exhibits a broad minimum near 100 K and then a slow increase while chi (perpendicular to)(T) shows a monotonic decrease. A sharp peak in C-p(T) at 4.7 K manifests an antiferromagnetic ordering. The electronic contribution, gamma, to C-p(T) is estimated to be gamma = 103.2 (7) mJ/mole.Sm.K-2. The entropy associated with the magnetic ordering is much smaller than Rln2, where R is the gas constant, which is usually expected for the doublet ground state of Sm+3. The unusual magnetic and electronic properties evident in M(T) and C-p(T) are probably due to a strong anisotropic interaction between conduction electrons and localized electrons at Sm+3 sites.