Ferromagnetism of anatase Ti1−XCoXO2−δ films grown by ultraviolet-assisted pulsed laser deposition

Abstract

We report the effect of ultraviolet irradiation during pulsed laser deposition on the growth of cobalt-doped TiO2 films in terms of the crystalline and magnetic properties. Due to more active oxygen gas species created by photodissociation and enhanced atomic migration on the substrate surface, highly crystalline films could be obtained at a relatively low deposition temperature of 400 °C. The full width at half maximum of the (004) peak rocking curve was 0.46° for the UV-assisted film deposited at 400 °C on the LaAlO3(001) substrate. Fourfold symmetry was observed in phi scans of the Ti0.93Co0.07O2−δ film, which indicated that this film was grown in cube-on-cube epitaxial orientation with the [001] normal to the LaAlO3(001) substrate surface. The temperature dependence of the zero-field-cooled/field-cooled magnetization was examined and the hysteresis was clearly identified by the nonzero difference between them. The Curie temperature was estimated to be well over 350 K, and at room temperature the coercive field was ∼180 Oe and the remanence was ∼17% of the saturation magnetization. The in-depth distribution of the constituent elements was characterized by Auger depth profiling. No segregation was found at the surface of the film and the interdiffusion between the substrate and the film was significantly reduced at the low deposition temperature used.