Spin-dependent localization effects in GaAs:Mn/MnAs granular paramagnetic-ferromagnetic hybrids at low temperatures

We compare the magneto-transport in paramagnetic-ferromagnetic GaAs:Mn/MnAs granular hybrids and paramagnetic GaAs:Mn reference samples. The differences in the hole transport between the two systems at low temperatures arise due to carrier localization effects at the cluster-matrix interface in the hybrids. The localization is caused by a Schottky barrier formation at the interface as well as spin-dependent shifts of the hole bands caused by the stray field of the ferromagnetic clusters. The application of an external magnetic field leads to a delocalization of the carriers and thus a negative magneto-resistance effect. These effects can be simulated using a network model approach.