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, Fe_2.4Ti_0.6O₄ and Fe₂TiO₄ measured at temperatures between 1.3° and 300°K. In Fe₃O₄, hopping occurs. In Fe_2.4Ti_0.6O₄, 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.