Magnetoresistance in pulsed laser deposited 3d transition metal doped ZnO films

ZnO films with different 3d transition metal doping (Ti, Co, Mn) were prepared by pulsed laser deposition. The occurrence of positive magnetoresistance (MR) was studied in dependence on temperature. Large positive MR was observed in Co- and Mn-doped ZnO films at 5 K. Zn0.98Mn0.02O films show a positive MR up to ∼ 31% at 5 K. The positive MR for Co- and Mn-doped ZnO films decreases drastically from 5 K to 50 K. Positive MR was also observed in Zn0.9998Ti0.0002O films at 290 K, while negative MR was observed at 5 K. Clear stripe-like magnetic domain pattern was observed by magnetic force microscopy for the Zn0.9998Ti0.0002O films, indicating the possible ferromagnetism at room temperature due to Ti3+-ions in a polarized spin state.