Ferromagnetism and structural defects in V-doped titanium dioxide

We report recent experimental results about influence of negatively charged structural defects on 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 1 at.%. The ferromagnetic order at room temperature (RT) was confirmed by SQUID magnetometry. Positron annihilation spectroscopy (PAS) was applied to check the presence of open-volume defects in the TiO2-δ matrix. The relation between ferromagnetic properties and amount of negatively charged defects in the studied films was established. The collection of structural, magnetometry, magnetotransport, magneto-optic and PAS data hints towards the defect-induced model of ferromagnetism in1 at.% V-doped TiO2-δ thin films.