Preparation, structure and ferromagnetic properties of the nanocrystalline Ti_1-x Mn_xO₂ thin films grown by radio frequency magnetron co-sputtering

This paper reported that the Mn-doped TiO₂ films were prepared by radio frequency (RF) magnetron co-sputtering. X-ray diffraction measurements indicate that the samples are easy to form the rutile structure, and the sizes of the crystal grains grow big and big as the Mn concentration increases. X-ray photoemission spectroscopy measurements and high resolution transmission electron microscope photographs confirm that the manganese ions have been effectively doped into the TiO₂ crystal when the Mn concentration is lower than 21%. The magnetic property measurements show that the Ti_1-xMn_xO₂ (x=0.21) films are ferromagnetic at room temperature, and the saturation magnetization, coercivity, and saturation field are 16.0emu/cm³, 167.5×80A/m and 3740×80A/m at room temperature, respectively. The room-temperature ferromagnetism of the films can be attributed to the new rutile Ti_1-xMn_xO₂ structure formed by the substitution of Mn⁴⁺ for Ti⁴⁺ into the TiO₂ crystal lattice, and could be explained by O vacancy (V_O)-enhanced ferromagnetism model.