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

Magnetic transport properties in Ti(1-x)CoxO(2) and Zn(1-x)CoxO magnetic semiconductors have been studied experimentally and theoretically. A linear relation of ln rho versus T-1/2 (. 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.