Tin- and titanium-doped γ-Fe₂O₃(maghemite)

Abstract

2.5% and 8% tin- and 8% titanium-doped γ-Fe2O3 have been synthesized and examined by x-ray powder diffraction, EXAFS, electron microscopy and by 57Fe- and 119Sn-Mössbauer spectroscopy. The Sn- and Ti-K-edge EXAFS show that both tin and titanium adopt octahedral sites in the spinel related γ-Fe2O3 structure. However, whereas tin substitutes for iron on one of the fully occupied sites, titanium adopts the octahedral site, which is only partially occupied. The 57Fe-Mössbauer spectra recorded in the presence of a longitudinal magnetic field of 2-8 T confirm that the tetravalent ions adopt the octahedral sites. The canting angles for both sublattices in γ-Fe2O3 were determined from the in-field Mössbauer spectra. The 119Sn-Mössbauer spectra showed that the maximum hyperfine field sensed by the Sn4+ ions in γ-Fe2O3 is about 2/3 of that observed in tin-doped Fe3O4 (magnetite).