Review of experimental and theoretical hyperfine parameters of 57Fe in iron TiO2 and SnO2 rutile systems

C. RODRIGUEZ TORRES; A. MUDARRA NAVARRO; L. A. ERRICO

Medellin

Congreso; XII Latin American Conference on Mossbauer Effect; 2012

Universidad de Antioquia, comite internacional LACAME

Conferencia invitada dictada por la Dra. C. Rodriguez Torres Fe-doped TiO2 and SnO2 are of significant interest in magnetism. Indeed, systems formed by the presence of magnetic ions in non-magnetic matrices (diluted magnetic semiconductors or diluted magnetic insulators, DMS or DMI) have attracted considerable interest in the last years due to their potential application in spintronic and magneto-optic devices. However, contradictory experimental as well as theoretical results were obtained, and it is uncertain whether the ferromagnetic signal (FM) found in some cases is intrinsic or comes from extrinsic magnetic phases. Conjectures were usually based on macroscopic experimental results but relatively little attention was given to the local structure around the dopants. The knowledge of the local environment of the dopant is essential to understand the mechanisms giving rise to magnetic order in these compounds. Here a review of our experimental and theoretical investigation of Fe-doped rutile TiO2 and SnO2 systems will be presented. The effect of oxygen vacancies on the hyperfine parameters, magnetic moments and the magnetic alignment for iron doped TiO2 and SnO2 is studied as a function of vacancy concentration and dopant distribution. The combined theoretical and experimental studies enable us to characterize the local structure around the iron impurities in rutile unambiguously and support the conclusion that oxygen vacancies are fundamental for the ferromagnetic response of these systems, explaining the diversity of magnetic moments observed experimentally for samples grown in different conditions.