Single-domain/multidomain bulk magnetic characteristics of Co-substituted Ni–Zn ferrites: tailoring the effect of Co substitution

The influence of cobalt ion substitution on the magnetic characteristics of Co x Ni 0.6− x Zn 0.4 Fe 2 O 4 ( x = 0.0 to 0.6) and the associated structural changes incurred in the bulk were investigated. The compositions were prepared by precursor combustion method and final sintered at 1000 °C to obtain bulk ferrites. The X-ray diffraction and Raman spectroscopic studies depict the formation of the ferrite phase and also confirm the retention of phase throughout substitution. The lattice parameter increases from 8.3849 to 8.4028 Ǻ with the increase in cobalt concentration, and by the virtue of higher ionic radii of Co 2+ ion than Ni 2+ ion that follows Vegard’s law. The study suggests redistribution of metal ions at the lattice sites, and the change in domain states favors changes in magnetic characteristics. Here, the saturation magnetization increases along with the enhancement in the hysteresis loop as the Co 2+ ion increases and was assigned to the higher magnetic moment of Co 2+ ion than Ni 2+ ion, as well as to the cationic redistribution. However, the permeability decreases with the Co ion substitution and was ascribed to microstructural changes and increased magnetocrystalline anisotropy. The permeability study also suggests the decrease in Curie temperature with the increase in cobalt content, and the AC susceptibility studies confirm the weakening of the A–B interaction.