Experimental and theoretical study of the dopant environment in Fe-doped TiO2 anatase nanoparticles

C. E. RODRÍGUEZ TORRES; L. A. ERRICO; A. F. CABRERA; F. REQUEJO; C. ADAN; S. J. STEWART

Foz de Iguazu

Congreso; XIV International conference on Hyperfine interactions & XIII International Symposium on Nuclear Quadrupole Interactions; 2007

Systems composed by the dilution of magnetic ions in semiconductor non-magnetic matrices (DMS) have attracted considerable interest in the last years due to potential application in spintronic devices. However, due to contradictory experimental as well as theoretical results obtained in DMS systems, it is uncertain whether the ferromagnetic signal found in some DMS is intrinsic one or comes from impurity magnetic phases. In particular, Fe-doped TiO2 with anatase and rutile structure is subject of this kind of  controversy. Even though a local technique as M¨ossbauer spectroscopy has been extensively employed to characterize the iron surroundings, the lack of a model to analyze the hyperfine parameters prevents a clear identification about the dopant location and, thus, contradictory results are found in the literature. In this work, by combining M¨ossbauer, x-ray absorption spectroscopies and ab initio calculations, we present an exhaustive characterization of the local structure of iron in TiO2 anatase nanoparticles synthesized by a  microemulsion method. Structural information and hyperfine parameters were obtained from first-principles calculations using the density-functional approach to compare with experimental results. We will show that combining these techniques with ab initio calculations enable us to unambiguously characterize the local environment of Fe impurities to further analyze its magnetic behavior.