Room-temperature ferromagnetism in Ti1-xVxO2 nanocrystals synthesized from an organic-free and water-soluble precursor

Ti1-xVxO2 nanocrystals were prepared by employing a novel and water-soluble precursor via hydrothermal method, and the microstructure and magnetic properties have been investigated. All the samples belong to a pure anatase structure and exhibit room-temperature ferromagnetism (RTFM) without any trace of vanadium oxides or clusters. After V doping, the anatase structure is retained, while crystal growth is restrained. The homogenous distribution of V, in V4+ chemical state, in TiO2 lattice is confirmed by X-ray powder diffraction (XRD), energy-dispersive X-ray spectra (EDS), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses. Ferromagnetism in Ti1-xVxO2 is revealed to be highly dependent on the V content and defect concentrations. Furthermore, the annealing study in various atmospheres indicates that the oxygen vacancies and interstitials play a crucial role in inducing ferromagnetism in Ti1-xVxO2 system, and the origin of RTFM can be explained by bound magnetic polaron model.