Local structure and magnetic behaviour of Fe-doped TiO2 anatase nanoparticles: Experiments and calculations

C. RODRÍGUEZ TORRES; A. F. CABRERA; L. ERRICO; C. ADAN; F. G. REQUEJO; M. WEISSMAN; S. J. STEWART

JOURNAL OF PHYSICS CONDENSED MATTER

Institute of Physics and IOP Publishing Limited

Año: 2008 vol. 20 p. 135210 - 135210

0953-8984

El artículo consta de 9 páginas. La referencia correc ta es:  <!-- /* Font Definitions */ @font-face {font-family:"MS Sans Serif"; panose-1:0 0 0 0 0 0 0 0 0 0; mso-font-charset:0; mso-generic-font-family:swiss; mso-font-format:other; mso-font-pitch:variable; mso-font-signature:3 0 0 0 1 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0pc; margin-bottom:.0001pt; mso-pagination:none; font-size:10.0pt; font-family:"MS Sans Serif"; mso-fareast-font-family:"Times New Roman"; mso-bidi-font-family:"Times New Roman"; mso-ansi-language:ES-TRAD; layout-grid-mode:line;} @page Section1 {size:51.0pc 66.0pc; margin:6.0pc 7.5pc 6.0pc 7.5pc; mso-header-margin:3.0pc; mso-footer-margin:3.0pc; mso-paper-source:0;} div.Section1 {page:Section1;} --> Journal of Physics: Condensed Matter 20, 135210-1 135210-9, 2008. We present an investigation of Fe-doped TiO2 anatase nanoparticles (2.8 and 5.4 at.% Fe) whereFe substitutes Ti atoms without the presence of other phases. In order to characterize thesesamples we used x-ray absorption experiments, 57Fe M¨ossbauer spectroscopy, ab initiocalculations and magnetometry. Results from iron K-edge near-edge and extended x-rayabsorption fine structure confirm that Fe3+ replaces Ti4+ in the TiO2 anatase structureincreasing the metal-anion bond length. M¨ossbauer spectra recorded at room temperature showasymmetric Fe3+ broad doublets. These results agree with structural, hyperfine and magneticproperties calculated using density-functional theory, if oxygen vacancies are present in theiron–oxygen octahedra. M¨ossbauer and magnetic measurements indicate that samples areparamagnetic at room temperature. At low temperatures, two kind of magnetic species can bedistinguished: (i) isolated paramagnetic Fe3+ ions and (ii) antiferromagnetically coupled Fe3+ions. These results also show that substitutional Fe in nanosized anatase TiO2 does not induceferromagnetic ordering.