Magnetic properties of disordered oxides with iron and manganese ions

Abstract Magnetic properties of disordered oxides involving oxide glasses have been investigated. Spin glass-like transition is observed for Fe 2 O 3 –TeO 2 and MnO–TeO 2 glasses in temperature dependence of dc susceptibility, although magnetic transition does not take place for MnO–TeO 2 glasses with low concentration of manganese ion above 2 K at least. The mechanism of magnetic transition observed for Fe 2 O 3 –TeO 2 glasses is discussed on the basis of dc susceptibility obtained under conditions of field cooling and zero field cooling, magnetic field dependence of magnetization at low temperatures, and frequency dependence of spin-freezing temperature derived from temperature dependence of ac susceptibility. Magnetic properties of disordered ZnFe 2 O 4 thin film prepared by a radio frequency sputtering method have been also studied. The disordered ZnFe 2 O 4 thin film exhibits ferrimagnetic behavior with high magnetization even at room temperature. At the same time, the thin film shows spin-freezing at around 320 K. Temperature dependence of nonlinear susceptibility leads to a conclusion that this transition is explainable in terms of superparamagnetism with magnetic interaction among clusters.