The geometric structure influence on the ferromagnetism in Carbon-doped anatase TiO2: First-principles study

First-principles calculations have been performed on the C-doped anatase TiO2. The doped TiO2 shows half-metallic properties and a 2.0 μB magnetic moment per cell. The magnetic coupling is closely related to the C-C distance. When the distance is shorter than a typical CC double bond (1.34Ǻ), the system is nonmagnetic and the dopants tend to form a cluster through a direct CC bonding interaction [Appl. Phys. Lett. 93 (2008) 132507]. When the distance is between 3.8 and 5.5Ǻ, there exists strong ferromagnetic or antiferromagnetic coupling between two C atoms. The ferromagnetic coupling is induced by the bent C-Ti-C unit. When the distance is further increased, the system becomes paramagnetic.