Microstructure-dependent magnetic properties of Li-Cd ferrites

Polycrystalline Li0.5-x/2CdxFe2.5-x/2O4 ferrites are prepared by a double sintering ceramic technique and characterized by X-ray diffraction. The lattice parameter increases monotonically with cadmium content, which is explained by the variation of tetrahedral and octahedral site ionic radii with cadmium content. Scanning electron microscopy micrographs reveal that the grain size increases up to x = 0.3 and then decreases for x > 0.3. A similar trend is observed in the variation of M-s with Cd2+ content. The decrease of M-s above 30% addition of cadmium is explained on the basis of the canted spin model. The initial permeability is found to increase continuously up to x = 0.6, and for x > 0.6, the sample shows a paramagnetic behavior. The increase in mu(i) above x = 0.3 is due to an abrupt decrease of K-1 with further increase in x. The initial permeability increases with increase in temperature and drops off sharply near T-c, which is explained by the variation of M-s and anisotropy constant with temperature. The continuous decrease of T-c with Cd2+ is attributed to the dilution of A-B interaction. (C) 1998 Elsevier Science Ltd.