Cations distribution by Rietveld refinement and magnetic properties of MgCrxFe2−xO4 spinel ferrites

Abstract

Magnesium–chromium ferrites MgCrxFe2−xO4 (0 ≤ x ≤ 1) were studied using X-ray diffraction and magnetization measurements. Rietveld refinement of XRD patterns confirmed the cubic spinel structure in the space group Fd-3m and enabled to obtain the cations’ distribution amongst octahedral and tetrahedral sites of this structure. Magnetization measurements were performed using vibrating sample magnetometer (VSM) in the temperature range of 300–700 K and superconducting quantum interference device (SQUID) in the range of 10–300 K. Hysteresis loops for each concentration x at 300 K, show non-linear variation of saturation magnetization (MS) with chromium content. Both coercitive field and remanence decrease with increasing chromium content. MS variations with temperature indicate that the Curie temperature TC decreases with increasing chromium content. On the basis of Neel’s two sub-lattice crystal field model, the cations’ distribution enabled to calculate the theoretical magnetic moments at 0 K which are compared and discussed with those extracted by extrapolation to 0 K from MS experimental data.