Appearance of ferromagnetism in co-doped CeO₂ diluted magnetic semiconductors prepared by solid-state reaction

We report on the magnetic and electronic properties of Co-doped CeO ₂ oxides prepared by a solid-state reaction. The as-prepared samples exhibit pure paramagnetic behavior, but postannealing at 450 °C for 1 h under H₂/N₂ atmosphere results in the appearance of ferromagnetism at room temperature. The electronic structure of as-prepared and postannealed Co-doped CeO₂ diluted magnetic oxides is investigated using soft X-ray absorption and emission spectroscopy. Co L-edge resonant inelastic X-ray scattering (RIXS) spectra indicate that direct Co-Co bonds form due to the precipitation of Co atoms in CeO₂. This is in agreement with zero-field-cooled and field-cooled thermal variations of the magnetization, which indicated the presence of Co clusters with size larger than 8 nm. © 2010 American Chemical Society.