LAUSR

A series of Li0.5 + zSbzLaxFe2.5−2z−xO4 spinel ferrites were prepared by a standard ceramic technique. All samples sintered at 1100 ∘C with a heating rate of 4 ∘C/min. A single-phase cubic spinel structure was confirmed by X-ray diffraction analysis with the appearance of small peaks that represent secondary phases. AC conductivity as a function of frequency and temperature was carried out. The calculated values of the activation energy approve the obtained results and indicate the semiconductor properties of the investigated samples. Due to large ionic radius, La3+ ions cannot completely substitute Fe3+ ions. These ions occupy grain boundaries instead of spinel lattice and form secondary phases after interaction with other ions present in grain boundaries. The magnetic parameters were calculated from the magnetic susceptibility data, in the temperature range 300–900 K at three different magnetic field intensities of 2160, 3000, and 3800 Oe. The data showed a decrease in the magnetic susceptibility till it reaches the Curie temperature (TC). The observed decrease in the Curie temperature with La content was explained on the basis of Neel’s model and the cation distribution. One recommends the use of such sample in the application that demands high resistivity and high Curie temperature.