Intrinsic structural distortion and exchange interactions in SmFe Cr O compounds.

The effect of substituting different amounts of magnetic metal Fe on the magnetic properties of SmFe Cr O (0 < < 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 ( , 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 ( and ) were determined. It was found that the strength of the symmetric interaction (reflected in the changes in the Neel temperature) increases with the replacement of Cr with Fe, which is ascribed to the changes in the average Cr(Fe)-O-Cr(Fe) bond angle and bond lengths. Meanwhile, the antisymmetric interaction a slightly decreases, which may be ascribed to the displacement of oxygen ions (dO) away from their "original" middle point.