Microstructure and magnetic properties of Li-Co ferrites

The microstructure and magnetic properties of Li0.5-x/2 COx Fe2.5-x/2 O-4 ( where x=0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7) ferrites have been reported. The ferrite samples were prepared by standard double sintering ceramic techniq ue and structural analysis was carried out using X-ray diffraction. The lat tice parameter (a) increases with increase in x. The average grain size obt ained from SEM micrographs shows an initial decrease up to x=0.4 and then i t increases. The saturation magnetization (M-s) and initial permeability (m u(i)) decrease with cobalt content up to x=0.4 and then a small increase is observed in case of mu(i). This has been attributed to high positive value of anisotropy constant (k(1)) for Co2+. The Curie temperature of the sampl es decreases with increase in the content of cobalt (x) due to reduction in the A-B interaction. The initial permeability of the samples remains almos t independent of frequency in the frequency range studied viz. 1 kHz to 1 M Hz. The measurement of AC susceptibility with temperature reveals the singl e domain (SD) state of the samples. (C) 2000 Elsevier Science S.A. All righ ts reserved.