Controllable spin-polarized electrical transport in wide-band-gap oxide ferromagnetic semiconductors

Abstract

A family of wide-band-gap ternary oxide ferromagnetic semiconductor films with high transition metal concentration was prepared. The resistivity of these films can be changed up to four orders of magnitude by varying the composition or the concentration of the oxygen vacancies. Moreover, all these films show common features in electrical transport, i.e., Mott variable range hopping (VRH) in the lower resistivity range, Efros VRH in the middle resistivity range, and “hard gap” resistance in the higher resistivity range. The above phenomena are well understood by considering the relative magnitude of three characterization lengths, i.e., Coulomb screening length, localization length of the carriers, and optimal hopping distance. Furthermore, spin polarization ratio of these magnetic semiconductors was obtained by fitting the experimental results of electrical transport. Therefore, the wide gap oxide ferromagnetic semiconductors with controllable spin-polarized electrical transport are expected to have application in spintronics devices as a spin injection source.