Unusual nature of electronic and magnetic states of Sm 1.85Ce 0.15CuO 4−δ

Abstract

Temperature-dependent magnetization ( M( T)) and specific heat ( C p( T)) measurements were carried out on single-crystal Sm 1.85Ce 0.15CuO 4−δ ( T c =16.5K). The magnetic anisotropy in the static susceptibility, χ ≡ M/ H, is apparent not only in its magnitude but also in its temperature dependence, with χ] for H ] c larger than χ| for H | c. For both field orientations, χ 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, χ|(T) exhibits a broad minimum near 100 K and then a slow increase while χ](T) shows a monotonic decrease. A sharp peak in C p( T) at 4.7 K manifests an antiferromagnetic ordering. The electronic contribution, γ, to C p( T) is estimated to be γ = 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.