EXPERIMENTAL EVIDENCE OF THE INFLUENCE OF THE CATION SITE OCCUPANCY AND OF ITS EVALUATION WITH THE TEMPERATURE ON THE MAGNETIC PROPERTIES OF SOFT FERRITES PREPARED BY WET METHODS

Mn-Zn ferrite prepared by wet methods show high reactivity : pressed samples reach almost theoretical density at temperatures lower than those usually required for sintering powders prepared by common ceramic techniques. They also show a largely different cation site occupancy which evolves with temperature approaching that of ceramic ferrites. Mossbauer spectra on MnFe2O4 also prepared by wet methods confirm such evolution which causes the magnetic moment at 0 K to shift from 4.11 to 4.60 µB as the temperature increases from 25 to 1 350 °C. The temperature dependence of magnetization with increasing Zn content for as prepared samples varies in a different way from that of samples annealed at 1 350 °C and quenched in water. The values of magnetic moments lower than those expected by the normal Neel theory of ferrimagnetism are explained rather well by a certain phenomenological evidence of a Yafet-Kittel effect.