Structure and Mössbauer Studies of F−O Ordering in Antiferromagnetic Perovskite PbFeO₂F

The synthesis of PbFeO 2 F is achieved using a solid-state reaction under high pressure. This perovskite crystallizes in SG Pm 3̄ m (No. 221) with a = 0.39991 (1) nm. The Rietveld refinement using powder X-ray diffraction data shows that the mean structure of this compound can be characterized as follows: (1) the Pb ion statically shifts from the 1 a Wyckoff position in the twelve 〈110〉 direction toward anions (O, F), and (2) the Fe ion is located in a single crystallographic site. In contrast, hyperfine data estimated from Mössbauer spectra at different temperatures suggest the existence of different Fe sites, and the isomer shift is consistent with the presence of high-spin (HS) Fe 3+ ions located in FeO 4 F 2 octahedral units, where anions are randomly distributed. Such a distribution thus favors two prevailing Fe sites, namely cis and trans. No evidence of O/F ordering in PbFeO 2 F was detected by electron diffraction experiments. Finally, in-field Mössbauer spectra unambiguously reveal that PbFe 2 OF behaves as an antiferromagnet, which is consistent with static magnetic measurements.