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 H 2 /N 2 atmosphere results in the appearance of ferromagnetism at room temperature. The electronic structure of as-prepared and postannealed Co-doped CeO 2 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 CeO 2 . 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.