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

2.5% and 8% tin- and 8% titanium-doped gamma -Fe2O3 have been synthesized and examined by x-ray powder diffraction, EXAFS, electron microscopy and by Fe-57- and Sn-119-Mossbauer spectroscopy. The Sn- and Ti-K-edge EXAFS show that both tin and titanium adopt octahedral sites in the spinel related gamma -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 Fe-57-Mossbauer 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 gamma -Fe2O3 were determined from the in-field Mossbauer spectra. The Sn-119-Mossbauer spectra showed that the maximum hyperfine field sensed by the Sn4+ ions in gamma -Fe2O3 is about 2/3 of that observed in tin-doped Fe3O4 (magnetite).