Effects of cation distribution on the magnetic and electrical properties of cobalt ferrite

Variation of the saturation magnetization, the electrical resistivity, the Hall parameters, and the Seebeck coefficient with quenching temperature was measured in cobalt ferrites, Co_xFe _3-xO₄ (x=0.94, 0.97, 1.00, and 1.03). With increasing quenching temperature, the saturation magnetization of cobalt ferrites increases and the electrical resistivity decreases. The Hall measurements indicate that the decrease in the electrical resistivity in cobalt ferrites is attributed to increase of the electron concentration. The conducting mechanism of cobalt ferrites, except for Co_1.03Fe_1.97O₄, is identified to be n-type. For Co_1.03Fe_1.97O₄, however, the conducting mechanism changes from p-type (for the furnace-cooled specimen) to n-type (for the specimens gas-quenched at 900 and 1200°C). The changes in the saturation magnetization, electron concentration, and Seebeck coefficient of cobalt ferrites by quenching heat treatment are related to the Fe ion migration from tetrahedral sites to octahedral sites and the charge conversion of the Fe ions accompanying site change