Exchange field on the rare earth Sm3⁺ in a single crystal perovskite SmMnO₃

Single crystal SmMnO₃ has been grown by the floating-zone method. We have measured the magnetization and specific heat in magnetic fields oriented along three principal crystal axes of precisely oriented single crystals. Below T_N of the Mn3⁺-ion array, the magnetic moments of the Sm3⁺ ions are progressively oriented antiparellel to the weak canted-spin ferromagnetic moment of the antiferromagnetic (AF) Mn3 ⁺-ion array due to an internal exchange field H_in. On cooling through a compensation temperature T_comp 9 K, the dominant moment parallel to c changes from the canted-spin Mn3⁺ ions to the Sm3⁺ moments. A spin reversal in an H_c 1 T changes the magnetic field splitting of the Kramers doublet on the Sm3⁺ ions from H_in - H_c to H_in + H_c, where H _c is a field applied along the c axis. This change, monitored by the Schottky contribution to the specific heat, creates an abrupt change at T _t = T_comp ± δ. We have found no evidence that the transition at T_t is first-order despite its abrupt nature. © 2011 American Physical Society.