Effects of cation distribution on superexchange interaction in cobalt ferrites

The effects of the cation distribution change on the superexchange parameters and magnetic properties of cobalt ferrite powders were investigated. The cation distribution change of cobalt ferrite powders with quenching treatment was confirmed from the Mossbauer experiments. The exchange interaction parameters, i.e. J/sub AA/, J/sub BB/ and J(AB), and Neel temperature of slow-cooled and quenched CoFe/sub 2/O/sub 4/ powders were calculated from the variation of the magnetization with temperature on the basis of the two-sublattice model. With a quenching treatment of CoFe/sub 2/O/sub 4/, the thermal magnetization was changed, and this was attributed to the cation distribution change of cobalt ferrites. The absolute values of J/sub AB/ increased with the quenching treatment of CoFe/sub 2/O/sub 4/, while those of J/sub AA/ and T/sub N/ decreased. The values of J/sub BB/ of cobalt ferrite remained the same with the quenching treatment. This result suggested that the decrease of T/sub N/ of CoFe/sub 2/O/sub 4/ with quenching may be attributed to the decrease of J/sub AA/.