Density functional study on ferromagnetism in nitrogen-doped anatase TiO2

We report first principles calculations on the magnetism and electronic structures for nitrogen-doped anatase TiO2 (N:TiO2). Our calculations indicate that magnetic state is the ground state for N:TiO2 systems. An isolated N atom produces a total magnetic moment of 1.00 mu(B) and introduces spin-polarized 2p states in the band gap. The origin of the magnetic moments is the holes in N 2p pi band of the N dopant. Several doping configurations studied suggest the existence of ferromagnetic coupling between N dopants. The ferromagnetism in N:TiO2 can be attributed to the hole-mediated double exchange through the strong p-p interaction between N and O.