Intrinsic structural distortion and exchange interactions in SmFe_:XCr_1-xO₃ compounds

The effect of substituting different amounts of magnetic metal Fe on the magnetic properties of SmFe_xCr_1-xO₃ (0 < x < 0.5) is reported here in order to probe the relation between the structural distortion and magnetism in these materials. The structural properties of the samples were characterized using X-ray diffraction with Rietveld refinements, and Raman spectroscopy carried out at ambient temperature. Magnetization data reveals the Neel temperature (T_N, where the Cr(Fe) ions order) increases with an increase in the average B-site ionic radius, and average Cr(Fe)-O-Cr(Fe) bond angle. By fitting the temperature dependence of the magnetic susceptibility to the Curie-Weiss law modified by the Dzyaloshinskii-Moriya (DM) interaction, the strengths of the symmetric and antisymmetric Cr(Fe)-Cr(Fe) exchange interactions (J and D) were determined. It was found that the strength of the symmetric interaction J (reflected in the changes in the Neel temperature) increases with the replacement of Cr³⁺ with Fe³⁺, which is ascribed to the changes in the average Cr(Fe)-O-Cr(Fe) bond angle and bond lengths. Meanwhile, the antisymmetric interaction D a slightly decreases, which may be ascribed to the displacement of oxygen ions (dO) away from their "original" middle point.