Abnormal Resistance and Magnetoresistance Temperature Dependence in Fe-Semiconductor Granular Films

A series of magnetic granular films using transparent semiconductor indium-tin oxide (ITO) as host were prepared. The dependence of magnetic, electrical properties, and magnetoresistance on Fe volume fractions and temperature are investigated. A magnetic transition from superparamagnetic granular film to ferromagnetic granular films with increasing the volume fraction of Fe is observed. For low Fe volume fraction samples, the field dependence of magnetoresistance could be well fitted by the weak interaction quadratic formula whereas for the samples of higher Fe volume fraction the interaction between magnetic granules plays an important role. The temperature dependence of resistivity and magnetoresistance ratio are also investigated. Metal--insulator/semiconductor transition is observed and an abnormal fluctuation behavior of resistance and MR ratio are found in high Fe volume fraction samples.