Ferromagnetism in Cu-doped ZnO films: Role of charge carriers

We report the observation of room temperature ferromagnetism in Cu-doped (5%) ZnO films grown on c-plane sapphire substrates. Films were prepared by pulsed laser deposition technique and were thoroughly characterized using several state-of-the-art characterization techniques. Hall measurements showed that the films are of n-type with a carrier concentration of 3x10(17) cm(-3). Magnetization measurements showed that the films exhibit room temperature ferromagnetism with a saturation magnetization of similar to 1.45 mu(B)/Cu atom. When additional carriers were introduced in the films, ferromagnetism was completely vanished. Our results show that the p-type nature of the film is not essential for realizing ferromagnetic characteristics; however, the concentration of n-type carriers should not exceed a critical value. (C) 2008 American Institute of Physics.