Mössbauer-Effect Measurements in FeTi Spinels with Local Disorder

Abstract

Local variations in hyperfine fields produce very broad lines in the Mössbauer spectra of FeTi spinels. These may result from two effects: (A) random variations of local symmetry at the iron sites which are characteristic of the local disorder and independent of temperature and (B) temperature-dependent electron hopping on the octahedral sites. We have studied these two processes in the 57Fe Mössbauer-Effect spectra of polycrystalline Fe3O4, Fe2.4Ti0.6O4 and Fe2TiO4 measured at temperatures between 1.3° and 300°K. In Fe3O4, hopping occurs. In Fe2.4Ti0.6O4, both hopping and local disorder influence the spectrum. In Fe2TiO4, hopping cannot occur and the broadening arises from local disorder. At low temperatures, the quadrupole splitting of the Fe+ + ions in octahedral sites in Fe3O4 was found to be −1.0 mm/sec.