Room-Temperature Ferromagnetism of Co-Doped CeO₂ Thin Films on Si(111) substrates

Using Co₂O₃ as the Co source, doped cerium oxide thin films with the composition of Ce_0.97Co_0.03O_2-δ (CCO) are deposited on Si(111) and glass substrates by pulse laser deposition technique. X-ray diffraction reveals that CCO films with (111) preferential orientation are grown on Si, while the film on glass is polycrystalline with nanocrystal. X-ray photoelectron spectroscopy shows that the Co displaces the Ce atom and exists in high spin state rather than low spin state, which contributes to the room-temperature ferromagnetism confirmed by vibration sample magnetometer. Films on Si and glass are different in ferromagnetism, which is believed to be induced by different film microstructures. Based on these results, the possible ferromagnetism in this insulating film is discussed. Anyway, successful fabrication of CCO films with room-temperature ferromagnetism on Si substrates is of great importance in both technological and theoretical aspects.