“Dopant local structure and magnetic behavior of Fe-doped TiO2 anatase nanoparticles”

C. R. TORRES, F. CABRERA, L. ERRICO, C. ADÁN, F. REQUEJO. M. WEISSMAN, S. J. STEWART

Campinas, Brasil

Workshop; 18ª Reunião Anual de Usuários. LNLS; 2008

LNLS

We present an investigation of the local structure of dopant sites and magnetic behavior of Fe-doped TiO2 anatase nanoparticles (2.8 and 5.4 at.% Fe) through x-ray absorption experiments, 57Fe Mössbauer spectroscopy, ab initio calculations and magnetometry. The iron K-edge near-edge and extended x-ray absorption fine structure results indicate that Fe(III) replaces Ti(IV) and causes an enlargement of metal-anion bonds length. Mössbauer spectra recorded at room temperature show asymmetric Fe3+ broad doublets. Structural, hyperfine and magnetic properties were investigated from first-principles calculations using the density-functional approach assuming that iron substitutionally replaces Ti in the anatase lattice. A good agreement between theory and experiment is achieved when anionic vacancies at the iron-oxygen octahedron are taken into account. Mössbauer and magnetic measurements indicate that a fraction of Fe3+ diluted in TiO2 remains paramagnetic down to low temperatures. Further, the emergence of magnetically isolated clusters is favored as the amount of dopant increases. We also showthat there is no evidence of a ferromagnetic order induced by the dopant.