Universal spin-dependent variable range hopping in wide-band-gap oxide ferromagnetic semiconductors

This paper proposes a universal spin-dependent variablerange hopping theoretical model to describe various experimentaltransport phenomena observed in wide-band-gap oxide ferromagneticsemiconductors with high transition metal concentration. Thecontributions of the `hard gap' energy, Coulomb interaction,correlation energy, and exchange interaction to the electricaltransport are considered in the universal variable range hoppingtheoretical model. By fitting the temperature and magnetic fielddependence of the experimental sheet resistance to the theoreticalmodel, the spin polarization ratio of electrical carriers near the Fermilevel and interactions between electrical carriers can beobtained.