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

Abstract

The synthesis of PbFeO2F is achieved using a solid-state reaction under high pressure. This perovskite crystallizes in SG Pm3̄m (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 1a 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) Fe3+ ions located in FeO4F2 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 PbFeO2F was detected by electron diffraction experiments. Finally, in-field Mössbauer spectra unambiguously reveal that PbFe2OF behaves as an antiferromagnet, which is consistent with static magnetic measurements.