ИСТИНА

Since the pioneering paper of Y. Matsumoto et al. [Y. Matsumoto et al., Science 291, 854 (2001)], the number of publications on TiO2 films doped by different 3d impurities, such as cobalt, iron, vanadium or manganese, is steadily increased. Up to now the most popular but competitive points of view on origin of ferromagnetism at RT are carrier-mediated and defect-induced models. We report recent experimental results about room-temperature ferromagnetism in V-doped TiO2- δ thin films with different electric conductivities. Films were prepared on LaAlO3 (001) substrates by RF magnetron sputtering in reduced argon–oxygen atmosphere, while the V to Ti metal ratio was fixed at 1at.% or 3at%. For Ti0.99V0.01O2-δ the direct relation between saturated magnetization probed by SQUID and the concentration of negatively charged structural defects probed by Positron Annihilation Spectroscopy (PAS) has been established [O. Yildirim et al., accepted to PSS]. The absence of magneto-optical transversal Kerr effect signal and the anomalous Hall effect supports the assumption of defect-induced origin of magnetism in the studied films without involvement of free charge carriers or the local magnetic moment of the V ion. For Ti0.97V0.03O2-δ the strong magneto-optical signal has been found with a huge difference in spectral shapes for films with different conductivities. The results of PAS are discussed. The workwas supported by a joint German-Russian project HRJRG-314 & RFBR 12-02-91321-SIGa