Electronic and Magnetic Properties of Electron-doped Superconductor, Sm_1.85Ce_0.15CuO_4-δ

Temperature-dependent magnetization [M(T)] and specific heat [Formula presented] measurements were carried out on single crystal [Formula presented] The magnetic anisotropy in the static susceptibility χ≡M/H is apparent not only in its magnitude but also in its temperature dependence, with [Formula presented] 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. With increasing temperature, however, [Formula presented] exhibits a broad minimum near 100 K and then a slow increase while [Formula presented] shows a monotonic decrease. A sharp peak in [Formula presented] at 4.7 K manifests an antiferromagnetic ordering. The electronic contribution, γ, to [Formula presented] is estimated to be [Formula presented] The entropy associated with the magnetic ordering is much smaller than [Formula presented] where R is the gas constant, which is usually expected for the doublet ground state of [Formula presented] The unusual magnetic and electronic properties evident in M(T) and [Formula presented] are probably due to a strong anisotropic interaction between conduction electrons and localized electrons at [Formula presented] sites.