Sol‒gel synthesis, structure, ferromagnetism and optical properties of Mn‒doped titania diluted magnetic semiconductors nanoparticles

Abstract

Diluted magnetic semiconductors composed of Ti 1-x Mn x O 2 nanoparticles, where x ranges from 0.0 to 0.1, were synthesized utilizing the sol-gel processing. X-ray diffraction (XRD), high resolution transmission electron microscopy, ultravioletvisible (UV-Vis) diffuse reflectance spectroscopy (DRS) and vibrating sample magnetometry (VSM) were used for structural, optical and magnetic characterization of the prepared nanomaterials. XRD revealed the coexistence of nanosized anatase and rutile phases with no secondary phase up to x= 0.07. When x= 0.1, a minority of secondary Mn 2 O 3 phase was detected. It was also found that increasing x, i.e. increase of Mn content, increased the anatase content at the expense of rutile, increased the cell parameters of both of anatase and rutile, and decreased the average crystallite nanosize of both of them. UV-Vis DRS absorption spectra exhibited peaks around 415-435 and 515 nm which corresponded to Mn 2+ and Mn 3+ ions, respectively. The band gap (E opt ) values suggest the semiconducting behavior for all the investigated compositions. E opt significantly decreased with increasing Mn concentration. VSM results indicated that pure titania is diamagnetic. While, all the studied Mn-doped TiO 2 compositions exhibited room temperature ferromagnetism. However, weaker ferromagnetism, shown by increased unsaturation, was observed with increasing Mn content.