Signature of intrinsic high-temperature ferromagnetism in cobalt-doped zinc oxide nanocrystals

The intrinsic nature of high-temperature ferromagnetism (FM) in cobalt doped nanocrystalline Zinc oxide powders was investigated. The existence of the satellite peak resembling CoO also suggests that the Co ions are primarily in a spin-spin electronic state. The low temperature synthetic method yields nanocrystalline material containing nanoparticles with a mean particle diameter of 53 nm. The arrangement is further verified by the high-resolution TEM (HRTEM) images taken at the edge of a nanoparticle. The local valence state of Co in the nanoparticle is further determined using EELS on a nanometer scale. A small increase in the binding energy of the Co-doped samples in comparison with the undoped one was observed with a shift in the binding energy of Zn 2p. the shift in the binding energy can be explained by the screening effect of electron after the bandbending effect is excluded by laser illumination.