Spin-dependent variable range hopping and magnetoresistance in Ti1−xCoxO2 and Zn1−xCoxO magnetic semiconductor films

Magnetic transport properties in Ti1−xCoxO2 and Zn1−xCoxO magnetic semiconductors have been studied experimentally and theoretically. A linear relation of lnρ versus T−1/2 (ρ is sheet resistance and T is temperature), which shows different slopes and intersections at different magnetic fields, was observed experimentally in the low temperature range. The spin-dependent variable range hopping model has been proposed by taking into account the electron–electron Coulomb interaction and the spin–spin exchange interaction in the same frame, which can well describe the observed magnetic transport properties in Ti1−xCoxO2 and Zn1−xCoxO magnetic semiconductors.