Room-temperature ferromagnetism in Mn-implanted TiO2

TiO2 single crystals were doped with Mn using the ion implantation technique at high doses leading to Mn concentrations of up to 7 at.% Mn. The Mn-doped TiO2 orders ferromagnetically above room temperature. The magnetic moment of the as-implanted samples (0.3 mu(B) per Mn) is reduced after thermal annealing at 400 degrees C under oxygen atmosphere due to a reduction of the oxygen deficiency. The moment recovers after annealing at higher temperatures reaching 0.4 mu(B) per Mn which indicates the incorporation of Mn atoms on substitutional sites. Electron spin resonance measurements show two types of signals which are independent of the orientation of the magnetic field corresponding to Mn2+ and Mn2+-O-Mn2+. In addition, four lines are strongly dependend on the orientation of the magnetic field and can be attributed to Mn4+.