Transition metal doped titania has been revealed as a promising diluted magnetic semiconductor. We report the synthesis of TiO2:Fe and of mixed Ti and Fe oxides by pulsed laser deposition. The obtained layers were analyzed by X-ray photoelectron spectroscopy, X-ray absorption fine structure and Kerr magnetometry. The magnetometry was performed in dark and by irradiating the sample, in order to probe the possibility of light control of ferromagnetism. Such control was obtained for some samples: the saturation magnetisation shows a clear decrease when iradiating. The complete explanation of this phenomenon needs additional insight on the electronic structure, chemistry and local atomic order. XPS revealed the chemical composition near the surface, which is close to Fe2Ti5O17 for samples with light-dependent saturation magnetisation, and Fe2Ti4O15 for samples where such dependence was not detected. XAFS evidenced the local atomic structure about Fe or Ti. For samples where conventional superparamagnetic behaviour was obtained, XAFS revealed the presence of metal Fe nanoparticles, whereas for samples where the light control of ferromagnetism occurs, a mixture of Fe-Ti oxides and Fe metal particles is inferred. The light influence on the magnetic properties is connected to the depletion of 3d states in the superparamagnetic nanoparticles.
Journal: TechConnect Briefs
Volume: 1, Nanotechnology 2009: Fabrication, Particles, Characterization, MEMS, Electronics and Photonics
Published: May 3, 2009
Pages: 249 - 252
Industry sector: Advanced Materials & Manufacturing
Topics: Advanced Materials for Engineering Applications