  Using the first-principles density-functional approach, magnetic properties
of Mn-, Fe-, Co-, and Ni-doped rutile TiO2 were investigated for two different
impurity concentrations (25% and 6.25%). Calculations were performed with the
Full-Potential Linearized-Augmented Plane Waves (FLAPW) method, assuming that
the magnetic impurities substitutionally replace the Ti ions. Our results show
that the systems (with the exception of Ni-doped TiO2) are ferromagnetic. We
also found that polarization mainly occurs at the impurity sites, and the
magnetic moments of the impurities are independent of the impurity
concentration.
