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.

► We carried out a systematic and detailed study on the structural and magnetic properties of Mn:TiO2 films with controlled Mn contents.
► Our results show that the magnetization of doped TiO2 increases exponentially with Mn content up to 5%, and then drop quickly with further increasing Mn content.
► The complex magnetic behavior of TiO2 with respect to Mn concentration is discussed based on the F-center exchange coupling mechanism.