Oxygen vacancy controlled tunable magnetic and electrical transport properties of (Li, Ni)-codoped ZnO thin films

We investigated the electrical, magnetic, and magnetotransport properties of Li-Ni codoped ZnO thin films in the electron dominated, hole dominated, and insulating regimes. In a narrow window of oxygen growth pressure, 10 -3 - 10-2 mbar, the films exhibited p-type conductivity with a maximum hole concentration ∼8.2× 1017 cm -3. Magnetoresistance exhibited by the films is attributed to scattering of charge carriers due to localized magnetic moments. Insulating films showed superparamagnetic behavior, whereas both n-type and p-type films showed room temperature ferromagnetism. Our findings suggest that oxygen vacancies and Ni ions in cation site are jointly responsible for ferromagnetism that is not dependent on the carrier type. © 2010 American Institute of Physics.