Hole mediated ferromagnetism in Cu-doped ZnO thin films on GaAs substrate

We studied the ferromagnetic properties and the relevant electronic structure of hole-doped ZnO:Cu films, using the element specific techniques of x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD). Hole-doping is achieved through As diffusion from the GaAs substrate to the deposited ZnO:Cu films, assisted by thermal annealing. The As-diffusion is probed with the help of XAS collected at the As K  -edge which shows enhanced signature of diffusion in the annealed samples. Cu charge state and the introduction of holes due to the As doping in ZnO:Cu films are investigated by the Cu L3,2L3,2-edge spectra. XMCD and magnetic measurements show that the magnetic moments originate from the doped Cu ions and that the magnetization is enhanced by the increase in As diffusion and hole doping which suggests a hole-mediated exchange interaction among the doped magnetic moments.

► Successful preparation of above room temperature ferromagnetic ZnO:Cu.
► Ferromagnetism is hole-mediated.
► Spectroscopic evidences for hole-doping and source of magnetism.