Electronic and Magnetic Properties of Electron-doped Superconductor, Sm_{1.85}Ce_{0.15}CuO_{4-delta}

摘要

Temperature-dependent magnetization (M(T)) and specific heat (C_p(T))measurements were carried out on single crystal Sm_{1.85}Ce_{0.15}CuO_{4-delta}(T_c = 16.5 K). The magnetic anisotropy in the static susceptibility, chi{equiv} M/H, is apparent not only in its magnitude but also in its temperaturedependence, with chi_{perp} for H{perp}c larger than chi_{parallel} forH{parallel}c. For both field orientations, chi does not follow the Curie-Weissbehavior due to the small energy gap of the J = 7/2 multiplet above the J = 5/2ground-state multiplet. However, with increasing temperature, chi_{parallel}(T)exhibits a broad minimum near 100 K and then a slow increase whilechi_{perp}(T) shows a monotonic decrease. A sharp peak in C_p(T) at 4.7 Kmanifests an antiferromagnetic ordering. The electronic contribution, gamma, toC_p(T) is estimated to be gamma = 103.2 (7) mJ/moleSmK^2. The entropyassociated with the magnetic ordering is much smaller than Rln2, where R is thegas constant, which is usually expected for the doublet ground state ofSm^{+3}. The unusual magnetic and electronic properties evident in M(T) andC_p(T) are probably due to a strong anisotropic interaction between conductionelectrons and localized electrons at Sm^{+3} sites.