Mössbauer Effect in the System Sr3Fe2O6–7

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Abstract
Previous studies of the Mössbauer effect for iron (IV) have been limited to the perovskitelike compounds SrFeO3 and BaFeO3. The structure of Sr3Fe2O7 is related, consisting of pairs of perovskite layers separated by a layer of strontium and oxygen ions. As in the previous studies of SrFeO3 and BaFeO3, samples of Sr3Fe2O6.9, Sr3Fe2O6.6, and Sr3Fe2O6.0 were prepared by equilibrating prereacted materials at various temperatures and oxygen pressures. Mössbauer spectra, measured at 298° and 4°K, indicated that the specimens of Sr3Fe2O6–7 are magnetically ordered at 4°K. The isomer shift of iron (IV) in Sr3Fe2O6.9 is −0.21 mm/sec at 298°K. The shift was more negative for the samples having a lower oxygen or iron (IV) content. Similarly at 4°K the magnetic hyperfine splitting went from 279 kOe for Sr3Fe2O6.9 to 232 kOe for Sr3Fe2O6.2. Quadrupole splitting was clearly evident in the trivalent component of these spectra and is attributed to the associated oxygen vacancy. The behavior is compared to that previously observed for systems containing iron (IV).
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