Laser reactivation of Room-T c ferromagnetism in Mn-doped insulating TiO2 thin films

Room-T c ferromagnetic insulating Mn-doped TiO2 thin films were prepared by plasma assisted molecular beam epitaxy (PAMBE). The thin films show obvious decay of ferromagnetism when aged in air at room temperature for one year without any special treatment. A distinct reactivation of ferromagnetism, together with a decrease in coercive force is achieved in these samples under laser irradiation treatment. The possible mechanism for the phenomena is also discussed. It is suggested that the bound magnetic polaron (BMP) forming via photo-generated defect-bound carriers accounts for the laser reactivation of room-T c ferromagnetism.