Magnetoresistance effects in Zn0.90Co0.10O films

Abstract

Zn 0.90 Co 0.10 O films of different thicknesses (689, 408, 355nm) doped with 0.5 at. % Al were prepared by pulsed laser deposition on a-plane sapphire substrates. At 290K the resistivity increases drastically with decreasing film thickness, while the electron concentration and mobility decrease. Magnetoresistance (MR) effects were measured in the temperature range of 5–290K. At low temperature, the positive MR increases with decreasing film thickness. Positive MR decreases rapidly with increasing temperature. With increasing temperature, the MR of the thicker film changes to negative, while positive MR was still observed for the 355nm thick film at 290K. Anomalous Hall effect was observed in the 355nm thick film at 20K, indicating the possible ferromagnetism in Zn0.90Co0.10O.