Pressure Effect of Sr₃Fe₂O_{6. 80} Studied by Mössbauer Spectroscopy

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The Mössbauer spectra have been measured for Sr₃Fe₂O_7-δ at ambient conditions and for Sr₃Fe₂O_{6. 80} under pressure. The iron sites are subdivided into two electronically nonequivalent states, that is, one is a tetravalent state and the other a trivalent one. The concentration and the isomer shift of tetravalent site depend on not only the oxygen vacancies but also pressure. It is found that the value of center shift exhibits a discontinuous decrease with increasing pressure and the change of pressure dependence around 8. 5 GPa