Investigation of structural, magnetic, electrical and optical properties of chromium substituted cobalt ferrites (CoCrxFe2−xO4, 0 ⩽ x ⩽ 1) synthesized using sol gel auto combustion method

The structural, magnetic, electrical and optical properties of chromium substituted cobalt ferrites (CoCrxFe2−xO4, x = 0.2, 0.4, 0.6, 0.8 and 1.0), have been investigated and on the basis of the saturation magnetization values, the cation distribution in the ferrite samples has been proposed. It is suggested that both Co2+ ions as well as Cr3+ ions seek to the octahedral sites of the ferrite sub-lattice. However, a small amount of Co2+ ions are also incorporated in the tetrahedral sites of the ferrite sub-lattice. This causes a decrease in the saturation magnetization (Ms) values with increasing Cr3+ concentration. The increase in Cr3+ ion composition in the ferrite sample decreases the value of saturation magnetization from 77 emu/g to 13 emu/g, indicative of the fact that the lesser magnetic Cr3+ ions substitute Fe3+ ions in the octahedral sub-lattice of the ferrites. A significant decrease in the saturation magnetization is observed in CoCrFeO4, attributing to the weakening of the A–B interaction as iron enters into the A site. The magnetic moments calculated from the proposed cation distribution (using Neel’s two sub-lattice model) are in conformity with those obtained from Ms values. The effect of annealing temperature on structural, magnetic, electrical and optical properties has also been investigated.