Molecular Field Theory of Magnetization in Rare Earth Orthochromites and Orthoferrites —Application to GdCrO₃—

Abstract

Molecular field equations for Γ₄, Γ₂₄ and Γ₂ phases of rare earth orthochromites and orthoferrites are derived and applied to the analysis of the observed magnetization in GdCrO₃. The Cr–Cr, Cr–Gd and Gd–Gd interactions are determined so as to fit the observed magnetization. The free energy is calculated by using these values of the parameters. It is shown that the single-ion anisotropy of the Gd³⁺ ion and the Gd³⁺–Gd³⁺ interaction contribute to the magnetization below 10 K and to the free energy below 3 K, while the Cr³⁺–Gd³⁺ antisymmetric exchange interaction stabilizes the free energy below 10 K.