Room temperature ferromagnetism in mixed-phase titania nanoparticles produced by the levitation–jet generator

Spherical mixed-phase titania nanoparticles with various ratios of anatase/rutile and an average size of 23–160 nm have been prepared by the levitation–jet aerosol generator through condensation of the Ti metal vapor in an inert gas flow with gaseous oxygen additive. The nanoparticles have been characterized by Scanning electron microscopy, Transmission electron microscopy, X-ray diffraction technique (XRD), Ultraviolet–Visible spectroscopy (UV–VIS), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and Vibrating sample magnetometry. Room temperature ferromagnetism with the maximum magnetization of up to 0.2 emu/g was discovered in the nanoparticles, wherein this magnetization was monotonically dependent on a product of three measured parameters of nanoparticles: specific surface, average particle size, and rutile content. The results indicate that the observed ferromagnetic ordering is related to the defect Ti–O structures at the interface between the both crystal phases of the nanoparticles. This suggestion is in good correlation with the number of characteristic spectroscopic data obtained during FT-IR, Raman, and XPS studies.