Doping effect of Cr3+ ions on the structural, magnetic and electrical properties of Co–Cd ferrites: A study on the redistribution of cations in CoCd0.4CrxFe1.6−xO4 (0.1 ≤ x ≤ 0.6) ferrites

Increasing chromium substitution in Co–Cd ferrites, synthesized via sol–gel auto-combustion method, remarkably influences their structural, magnetic and electrical properties. As the Cr3+ concentration is increased, various interesting changes in the values of structural parameters like X-ray density, bulk density and porosity have been observed. The value of lattice constant, is found to be ∼8.38 Å with an average crystallite size of ∼50 nm. The porosity in the entire ferrite samples is low (5.3%–6.9%). The magnetic properties, like saturation magnetization and coercivity, show a decrease trend with increase in Cr3+ concentration. The proposed cation distribution is further substantiated by the electrical properties. It is observed that the d.c. resistivity increases with Cr3+ concentration, suggesting occupancy of Cr3+ ions in the B-sites which leads to the dilution of Fe2+–Fe3+ conduction. The activation energy calculated from the d.c. resistivity vs temperature curves is found to be ∼0.25 eV.