X-ray, SEM and magnetic properties of Mg-Cd ferrites

Magnetic properties of polycrystalline ferrites CdxMg1-xFe2O4 (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) are studied for their saturation magnetisation n(B), AC susceptibility chi and initial permeability mu(i). Dependence of saturation magnetisation on Cd2+ content suggest that A-B and B-B superexchange interactions are comparable in strength. Neel's two sublattice model is applicable upto x less than or equal to 0.4 while Y-K three sublattice model is predominent for x > 0.4. Variation of AC susceptibility and initial permeability with temperature revealed the long-range ferrimagnetic ordering in the compounds having x less than or equal to 0.4. The sample with x less than or equal to 0.2 exhibits, multidomain structure, while for x = 0.4 shows SD-SP transition and for x greater than or equal to 0.6 the samples show S-P domain structure. Low-frequency dispersion of initial permeability suggests domain wall displacement. Addition of Cd2+ results in the sharp decrease in crystallographic phase transition temperature T-p and Curie temperature T-c of the samples.