Transformation of electrical transport from variable range hopping to hard gap resistance in Zn1−xFexO1−v magnetic semiconductor films

Transformation of the electrical transport from the Efros and Shklovskii J. Phys. C 8, L49 1975 variable range hopping to the “hard gap” resistance was experimentally observed in a low temperature range as the Fe compositions in Zn1−xFexO1−v ferromagnetic semiconductor films increase. A universal form of the resistance versus temperature, i.e., exp TH /T+ TES/T 1/2 , was theoretically established to describe the experimental transport phenomena by taking into account the electron-electron Coulomb interaction, spin-spin exchange interaction, and hard gap energy. The spin polarization ratio, hard gap energy, and ratio of exchange interaction to Coulomb interaction were obtained by fitting the theoretical model to the experimental results. Moreover, the experimental magnetoresistance was also explained by the electrical transport model. © 2006 American Institute of Physics. DOI: 10.1063/1.2386925