Abstract

A theory of spin-polarized transport in inhomogeneous magnetic semiconductors is developed and applied to magnetic/nonmagnetic p-n junctions. Several phenomena with possible spintronic applications are predicted, including spin-voltaic effect, spin valve effect, exponential and giant magnetoresistance. It is demonstrated that only nonequilibrium spin can be injected across the space-charge region of a p-n junction, so that there is no spin injection (or extraction) at low bias.