On the possibility of ferromagnetism in carbon-doped anatase TiO2

To see if ferromagnetism can occur in C-doped anatase TiO(2), we performed first-principles calculations for a number of C-doped structures in which C atoms substitute O atoms. Our study shows that each C has spin-polarized 2p states in the band gap generating a magnetic moment of 2.0 mu(B). The magnetic coupling between doped C atoms is substantial leading to either antiferromagnetism or ferromagnetism when the C center dot center dot center dot C distance lies between 3-4 angstrom. A strong ferromagnetic coupling occurs when the two C atoms form a slightly bent C-Ti-C unit by replacing two oxygen atoms at the opposite vertices of a TiO(6) octahedron. (C) 2008 American Institute of Physics.