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Zn_(0.95)Co_(0.05)O and Zn_(0.91)Co_(0.05)Cu_(0.04)O thin films were fabricated on Si(111) substrate by the reactive magnetron sputtering method at different O-Ar ratios.Detailed characterizations by X-ray diffractometry(XRD),X-ray photo-electronic spectrum(XPS), and electron paramagnetic resonance(EPR) indicate that the doped Cu ions substitute the Zn~(2+) ions in the ZnO lattice.The doped Cu ions are in Cu~+ and Cu~(2+) mixture valence states.The ferromagnetism of the Zn_(0.91)Co_(0.05)Cu_(0.04)O film increases gradually the increasing Cu~+ ions concentration.The results indicate that the increase of ferromagnetism is not owing to the magnetic contribution of Cu~+ ions themselves,but owing to the enhancement of magnetic interaction between Co ions,which suggests that p-type doping of Cu~+ ions plays an important role in mediating the ferromagnetic coupling between Co ions.
(0.95) Co_ (0.05) O and Zn_ (0.91) Co_ (0.05) Cu_ (0.04) O thin films were fabricated on Si (111) substrates by the reactive magnetron sputtering method at different O-Ar ratios.Detailed characterizations by X -ray diffractometry (XRD), X-ray photo-electronic spectrum (XPS), and electron paramagnetic resonance (EPR) indicate that the doped Cu ions substitute the Zn ~ (2+) ions in the ZnO lattice. in Cu ~ + and Cu ~ (2+) mixture valence states. The ferromagnetism of the Zn_ (0.91) Co_ (0.05) Cu_ (0.04) O films increases gradually the increasing Cu ~ + ions concentration.The results indicate that the increase of ferromagnetism is not due to the enhancement of magnetic interaction between Co ions, which suggests that p-type doping of Cu ~ ions plays an important role in mediating the ferromagnetic coupling between Co ions.