A study of magnetic clusters in Co-doped ZnO using neutron scattering

We report on a study of magnetic cluster in Co-doped ZnO using neutron diffraction. The samples are fabricated by the sol-gel process and the structural properties are characterized by X-ray diffraction and neutron diffraction. The diffraction data obtained by neutron are compared with the results of X-ray diffraction and refined by the Rietveld refinement method. The secondary phases are detected by neutron diffraction in above 5 mol% Co-doping of ZnO samples and the fractions of the phases in the samples are calculated. In particular, the Co metal phase is clearly observed in 30 mol% Co-doped ZnO. However, these secondary phases are not detected by X-ray diffraction due to reasons such as X-ray absorption by Co K-edge and incoherent X-ray scattering. We discuss the advantage of using neutron diffraction in studying the secondary phase and suggest the solubility limit of Co-doping.