Room temperature ferromagnetism in sol–gel prepared Co-doped ZnO

We report on the high temperature ferromagnetism in Co-doped ZnO samples with 2%, 4% and 6% nominal Co concentrations prepared by the sol–gel method. X-ray diffraction and X-ray photoelectron spectroscopy analyses confirm the absence of metallic Co clusters or any other impurity phases different from wurtzite-type ZnO. It is also observed that Co has occupied Zn sites. UV–visible absorption studies show an increase in band gap with Co concentration. The field dependence of magnetization exhibited clear ferromagnetism at room temperature with saturation magnetization and coercive field of the order of 0.0066–0.0239 emu/g and 149.09–40.31 Oe, respectively. Increase of saturation magnetization value with Co doping indicated that the ferromagnetism in the samples may be due to percolation of bound magnetic polarons.