Influence of rare earth moment ordering on magnetic entropy change in Nd0.5Sr0.5CoO3

Field-cooled magnetization of Nd0.5Sr0.5CoO3 shows an anomalous maximum at T* = 76 K << T-C = 228 K, where T-C is the ferromagnetic Curie temperature of the Co-sublattice. While T* shows a systematic shift with increasing magnetic field(H), the maximum does not disappear even at H = 7 T. We suggest that Nd(4f) moment is polarized by the molecular field of Co sublattice and order antiparallel to the Co(3d) spin lattice below T*, which causes magnetic entropy to decrease (increase) with increasing H for T > T* (T below T*). Critical exponents associated with the ferromagnetic phase transition were analyzed and found to be close to the mean-field model values. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4738889]