THE ORIGIN OF ROOM TEMPERATURE FERROMAGNETISM IN Co-TiO₂ SYSTEM

Abstract

The annealing effects on the composition, structure and magnetism for Co overlayer deposited onto rutile TiO 2 (100) surfaces at room temperature has been investigated. Room temperature ferromagnetic behaviour is exhibited for all samples, but saturation magnetic moment per Co atom decreases with increasing annealing temperature until 530°C. In-situ photoemission studies show that the reduction of the saturation magnetic moment is due to Co oxidation at high annealing temperature. However, the saturation magnetic moment increases after annealing the sample up to 700°C. The formation of a Co - Ti - O phase rather than Co metallic clusters observed by high-resolution transmission electron microscopy is suggested to be responsible for the increase of the saturation magnetic moment.