Transport properties of magnetic semiconductors: The weak coupling situation

Abstract

We examine the consequences for the transport properties of the exchange interaction between carriers in a relatively wide band and localized magnetic moments, with special reference to the properties of europium compounds. In section 2, the model of indirect exchange will be recalled. In section 3, the variation of carrier mobility with temperature and magnetic field will be studied, including (i) the spin-disorder scattering which leads to critical resistance and to negative magnetoresistance and (ii) the modifications in other scattering mechanisms which arise from the exchange interaction. We will analyze in section 4 how the exchange interaction induces or enhances the localization of a carrier around a charged impurity, leading to a magnetization dependence of the conductivity activation energy. Finally, in section 5, the role of magnetic disorder in the conduction process will be discussed. Throughout this review, the role played by non-diagonal linear response functions (e.g., response of the electronic system to magnetic field perturbations) will be emphasized.