Magnetic Properties of Fe Doped, Co Doped, and Fe+Co Co-Doped ZnO

The structural, electronic and magnetic properties of Zn0.95Co0.05O, Zn0.95Fe0.05O and Zn0.90Fe0.05Co0.05O nanoparticles prepared by a sol-gel method are presented and discussed. Xray diffraction and optical analysis indicated that high spin Co ions substitute for the Zn ions in tetrahedral sites. Fe Mössbauer spectroscopy showed the presence of isolated paramagnetic Fe ions in both Fe doped and Fe+Co co-doped ZnO, however, no evidence of ferromagnetically ordered Fe ions is observed. In the Zn0.95Fe0.05O sample, weak presence of ZnFe2O4 was detected as an impurity phase, whereas Zn0.90Fe0.05Co0.05O was impurity-free. Results of these studies suggest that Fe and Co ions in the Fe+Co co-doped sample has a strong synergistic effect because they eliminated the presence of impurities and gave the strongest ferromagnetic signal. Possible role of charge transfer ferromagnetism involving mixed valence ions is considered as a potential mechanism in these nanoparticles. Presence of both Co and Fe might promote more efficient charge transfer in the co-doped Zn0.90Fe0.05Co0.05O, leading to the enhanced ferromagnetism observed in this sample. However, more evidence is necessary to confirm the role of charge transfer ferromagnetism. This is an author-produced, peer-reviewed version of this article. The final, definitive version of this document can be found online at The Journal of Applied Physics, published by American Institute of Physics (AIP). Copyright restrictions may apply. DOI: 10.1063/1.4799778