Enhancement of ferromagnetism in Zn0.95Co0.05O films by lithium codoping

Zn0.95-xCo0.05LixO (x=0-0.12) thin films were synthesized by sol-gel method. Magnetic investigation showed that the ferromagnetism of the Zn0.95-xCo0.05LixO films increased with Li doping within the solubility limit of 9% but dropped sharply when x > 9% owing to the presence of the second-phase LiCoO2. X-ray diffraction, UV-visible absorption spectrum (UV-vis), Raman spectrum (Raman), and electrical resistivity investigation indicated that the Li-doping process in Zn0.95Co0.05O was of three stages. The structure and magnetic properties of Zn0.95-xCo0.05LixO films had different change trends in different stages. It was found that not only Li-Zn' related defects but also Li+ interstitials played important roles in enhancing the magnetic interaction between Co2+ ions, which was supported by the bound magnetic polaron model. (C) 2009 American Institute of Physics. [doi:10.1063/1.3202390]