Structural and magnetic properties of Mn:TiO2 films grown by plasma-assisted molecular beam epitaxy

Single-phase Ti1−xMnxO2 films with x = 0–8% were synthesized by plasma-assisted molecular beam epitaxy (PAMBE), and the effect of Mn content on the magnetic behaviors has been systemically investigated. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) studies indicate no Mn metal clusters or secondary magnetic phases in any samples in this study. It is found that the undoped or slightly doped samples show no ferromagnetic signal, while samples with x in the range of 3–5% exhibit an exponential increase of saturation magnetization (Ms) as a function of Mn concentration. When x increases beyond 5%, an inverse correlation between the magnetization and Mn content was observed. Our results also strongly support the oxygen vacancy (F-center) mediated mechanism for RT ferromagnetism in transition-metal doped high-k oxides.