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

Abstract

Single crystal SmMnO${}_{3}$ 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 Mn${}^{3+}$-ion array, the magnetic moments of the Sm${}^{3+}$ ions are progressively oriented antiparellel to the weak canted-spin ferromagnetic moment of the antiferromagnetic (AF) Mn${}^{3+}$-ion array due to an internal exchange field ${H}_{\mathrm{in}}$ \ensuremath{\parallel} $c$. On cooling through a compensation temperature ${T}_{\mathrm{comp}}$ \ensuremath{\approx} 9 K, the dominant moment parallel to $c$ changes from the canted-spin Mn${}^{3+}$ ions to the Sm${}^{3+}$ moments. A spin reversal in an ${H}_{c}$ \ensuremath{\ge} 1 T changes the magnetic field splitting of the Kramers doublet on the Sm${}^{3+}$ ions from ${H}_{\mathrm{in}}$ \ensuremath{-} ${H}_{c}$ to ${H}_{\mathrm{in}}$ $+$ ${H}_{c}$, 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 ${T}_{t}$ $=$ ${T}_{\mathrm{comp}}$ \ifmmode\pm\else\textpm\fi{} \ensuremath{\delta}. We have found no evidence that the transition at ${T}_{t}$ is first-order despite its abrupt nature.