Magnetic Properties of LnMnO3 (Ln=Ho, Er, Tm, Yb, and Lu)

Magnetic data are presented for LnMnO₃ (Ln=Ho, Er, Tm, Yb, and Lu) having the hexagonal crystal structure of P6₃cm. DC magnetization measurements show that magnetic order is not clearly observed for Ln=Ho-Yb, while an antiferromagnetic transition of the Mn³⁺ moments is found at ∼90 K for LuMnO₃, where the Lu³⁺ ion has no 4f localized moment. This is ascribed to both the paramagnetism of Ln³⁺ and the suppression of magnetization in the Mn³⁺ sublattices arising from strong antiferromagnetic interactions between Mn³⁺. Deviation from the Curie-Weiss law at low temperatures indicates the onset of antiferromagnetism. Some magnetization data of Ca-substituted compounds, Ln_0.5Ca_0.5MnO₃, which have the different crystal structure of orthorhombic Pnma, are also discussed briefly.