Vacuum Annealing Induced Room-Temperature Ferromagnetism in Co_0.1Ti_0.9O_2-δ Films Prepared by Sol-Gel Method

The Co-doped TiO₂ films (Co_0.1Ti_0.9O_2-∆) are prepared on silicon substrates by sol-gel method and post annealing. The Co_0.1Ti_0.9O_2-∆ film annealed in air is non-ferromagnetic at room temperature. After further annealed in a vacuum, the room-temperature ferromagnetism (RTFM) is observed. Experimental evidences show that the RTFM in the Co_0.1Ti_0.9O_2-∆ film may come from the Co-doped TiO₂ matrix and is related to the oxygen vacancies created by vacuum annealing.