Origin of room-temperature ferromagnetism in Co-doped CeO2

Co-doped CeO2 fabricated using the conventional solid-state reaction method demonstrates ferromagnetism at room temperature (RT). To investigate the origin of ferromagnetism at RT, powder X-ray diffraction analysis is first performed, in which pattern changes due to Co doping are not indicated. Subsequently, local environment analysis is carried out using X-ray absorption near-edge structure (XANES) measurements at the Co K-edge, demonstrating the metallic valence state of Co. Hence, it is confirmed that Co exists as nanosized small particles in CeO2, which demonstrates ferromagnetism at RT. •Origin of the room temperature ferromagnetism is nano-sized metallic Co in Co-doped CeO2.•Local environment of dilute Co was determined by X-ray absorption near edge structure measurements.•Sintering and annealing conditions are sensitive to the ferromagnetism in Co-doped CeO2.