The magnetic susceptibility, specific heat and dielectric constant of hexagonal YMnO₃, LuMnO₃ and ScMnO₃

Abstract

We report the magnetic susceptibility, specific heat and dielectric constant for high-purity polycrystalline samples of three hexagonal manganites: YMnO₃, LuMnO₃ and ScMnO₃. These materials can exhibit a ferroelectric transition at very high temperatures (T_FE>700 K). At lower temperatures there is magnetic ordering of the frustrated Mn³⁺ spins (S = 2) on a triangular Mn lattice (YMnO₃: T_N = 71 K; LuMnO₃: T_N = 90 K and ScMnO₃: T_N = 130 K). The transition is characterized by a sharp kink in the magnetic susceptibility at T_N below which it continues to increase due to the frustration on the triangular lattice. The specific heat shows one clear continuous phase transition at T_N, which is independent of external magnetic field up to 9 T with an entropy content as expected for Mn³⁺ ions. The temperature-dependent dielectric constant displays a distinct anomaly at T_N.