Mössbauer Study of Electron Hopping in the Octahedral Sites of Fe3O4

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Abstract
A linewidth study of the Mössbauer spectra of 57Fe in A and B sites in Fe3O4 as a function of temperature has shown that relaxation effects due to electron hopping in the B sites are present. It is found that the linewidth of 57Fe in A sites is temperature independent, whereas that in B sites decreases rapidly with increasing temperature. Above room temperature, the temperature dependence of the B‐site linewidth yields an activation energy close to that obtained by conductivity measurements just above the Verwey transition. Between the Verwey transition temperature and room temperature, the activation energy found from the B‐site line width is considerably less than that above room temperature. These data indicate that there are two processes which influence the Mössbauer spectra. It is also found that below the Verwey transition temperature, the spectrum due to 57Fe in B sites cannot be interpreted as being due to one six‐line spectrum for Fe2+ and another for Fe3+. This spectrum can be explained by assuming two Fe2+ spectra with an intensity ratio of 2:1.