Sign reversal of magnetoresistance and p to n transition in Ni doped ZnO thin film

We report the magnetoresistance and nonlinear Hall effect studies over a wide temperature range in pulsed laser deposited Ni0.07Zn0.93O thin film. Negative and positive contributions to magnetoresistance at high and low temperatures have been successfully modeled by the localized magnetic moment and two band conduction process involving heavy and light hole subbands, respectively. Nonlinearity in the Hall resistance also agrees well with the two channel conduction model. A negative Hall voltage has been found for T $\gte 50 K$, implying a dominant conduction mainly by electrons whereas positive Hall voltage for T less than 50 K shows hole dominated conduction in this material. Crossover in the sign of magnetoresistance from negative to positive reveals the spin polarization of the charge carriers and hence the applicability of Ni doped ZnO thin film for spintronic applications.