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 $H_{\mathrm{in}}$ ∥ $c$. On cooling through a compensation temperature $T_{\mathrm{comp}}$ ≈ 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 $H_c$ ≥ 1 T changes the magnetic field splitting of the Kramers doublet on the Sm${}^{3+}$ ions from $H_{\mathrm{in}}$ − $H_c$ 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 $T_t$ $=$ $T_{\mathrm{comp}}$ ± δ. We have found no evidence that the transition at $T_t$ is first-order despite its abrupt nature.

• Received 29 April 2011

DOI:https://doi.org/10.1103/PhysRevB.84.104415