Room temperature ferromagnetism in Nd- and Mn-codoped ZnO films

Nd and Mn were codoped into ZnO films which have been grown on a-plane sapphire substrates by pulsed laser deposition with the thickness ranging between 46 and 971 nm. The room temperature resistivity of the codoped films is independent of film thickness. Large positive magnetoresistance and clear anomalous Hall effect were observed at 5K. Ferromagnetism with clear hysteresis up to 290K was observed. Codoping is suggested to be an efficient method to introduce energy levels in the ZnO band gap to mediate the electron spins of the magnetic doping ions.