Electronic and magnetic properties of the electron-doped superconductor Sm1.85Ce0.15CuO4-δ -: art. no. 214504

Temperature-dependent magnetization [M(T)] and specific heat [C-p(T)] measurements were carried out on single crystal Sm1.85Ce0.15CuO4-delta (T-c=16.5 K). The magnetic anisotropy in the static susceptibility chi equivalent toM/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 toc. 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. With increasing temperature, however, chi (parallel to)(T) exhibits a broad minimum near 100 K and then a slow increase while X-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 R In 2, 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.