Influence of Co2+ on the electrical and magnetic properties of Li–Sb ferrites

Abstract Investigations have been carried out on the electrical properties of polycrystalline Li–Sb ferrites, when successively substituted with Co2+ ions. The samples with compositions Li0.6−0.5xCoxSb0.1Fe2.3−0.5xO4, (0.0≤x≤1.0 in steps of 0.2) were prepared by the double sintering ceramic technique. XRD method confirmed all the samples to be single-phase spinels. The decrease in resistivity is reported as a function of composition and temperature. The decrease in resistivity with composition has been attributed to the cation distribution and the presence of cobalt ions in the two valence states at the octahedral site. All the samples exhibit a change in slope in the plot of resistivity vs. inverse temperature, giving two regions with a large variation in activation energy. A dispersion with frequency was observed in the dielectric behaviour of all the samples, studied in the frequency range of 100 Hz to 1 MHz. Peaks were observed in the tan δ vs. frequency curve for all the samples x=0.4 and 0.8. The possible mechanisms involved are discussed. The observed decrease in the Curie temperature with cobalt content and the compositional dependence of room temperature saturation magnetization are explained on the basis of Neel's model and the cation distribution.