Effect of Fe doping on magnetoresistance and exchange coupling of Fe-doped ITO films

The magneto-transport properties of Fe-doped ITO films with various carrier concentrations ranging from 2.1 × 1019 to 1.7 × 1018 cm−3 were investigated systematically. Temperature dependent resistivity data suggested the conduction mechanism is dominated by Mott variable range hopping (VRH) behavior at low temperature, confirming that the carriers are strongly localized. The magnetoresistance (MR) behavior systematically depends on Fe doping and carrier concentration. The low Fe-doped ITO films with high carrier concentration only show a negative MR component at different temperatures, whereas high Fe doped films with low carrier concentration switch the MR sign and the positive MR component dominates at high field at 10 K. The MR data could be well fitted by presuming the spin-dependent scattering due to the third-order s-d exchange interaction for the negative MR and a two spin split subband model for the positive MR contribution. These results suggest that the Fe doping can remarkably tune the band structure and exchange interaction in wide band gap oxides.