Hole mediated ferromagnetism in Cu-doped ZnO thin films
  We report the successful synthesis of ZnO:Cu thin films doped with holes, resulting in room temperature ferromagnetism. Hole doping is achieved by As-diffusion from the GaAs substrate into ZnO films, assisted by thermal annealing. The As-diffusion is probed with the help of x-ray absorption spectra collected at the As K-edge which show enhanced signature of diffusion in the annealed samples. Introduction of holes, due to the As doping, in ZnO films is further evidenced by the Cu L3,2-edge spectra. XMCD and magnetic measurements show that the ferromagnetic interaction between doped Cu ions is enhanced after hole doping. 
Abhinav Pratap Singh, B.-G. Park, Ik-Jae Lee, Kyu Joon Lee, Myung-Hwa   Jung, Jinhee Kim, and J.-Y. Kim
cond-mat.mes-hall