AgFeOF₂: A Fluorine-Rich Perovskite Oxyfluoride

Abstract

We synthesized a silver iron oxyfluoride AgFeOF by using a high-pressure reaction. Synchrotron X-ray and neutron diffraction, X-ray absorption, and Fe Mössbauer spectroscopy indicate that AgFeOF crystallizes in the ideal perovskite structure with iron in a trivalent state, although electron microscopy revealed weak super-reflections. A possible partial ordering in the FeOF octahedron is inferred from Mössbauer spectroscopy. The synthesis of the fluorine-rich sample offers an opportunity to study a composition-property relation in AFeOF ( n = 0, 1, and 2). AgFeOF exhibits a G-type antiferromagnetic ordering below T ≈ 480 K, which is much lower than the n = 0 and 1 cases, suggesting a weaker superexchange interaction between Fe moments via F 2p orbitals (vs O 2p orbitals).

Anion Doping of Ferromagnetic Thin Films of La0.74Sr0.26MnO3−δ via Topochemical Fluorination

“…In this regard, F − doping may trigger antiferromagnetic coupling or extinguish any exchange interaction between adjacent Mn ions. This observation is in principle agreement with the recently reported weakening of Fe-F-Fe superexchange interactions as compared to Fe-O-Fe for the series LaFe 3+ O 3 F 0 (T N ~750 K), (Sr/Ba/Pb) Fe 3+ O 2 F 1 (T N = 650–700 K) and AgFe 3+ O 1 F 2 (T N ~500 K) [40], as well as the weakening of Ni-F-F-Ni superexchange interactions in La 2 Ni 2+ O 3 F 2 (T N = 49 K) as compared to Ni-O-O-Ni in La 2 NiO 4 (T N = 330 K) [14]. …”

Topochemical Reduction of La2NiO3F2: The First Ni-Based Ruddlesden–Popper n = 1 T′-Type Structure and the Impact of Reduction on Magnetic Ordering

“…[32][33][34] Further, superexchange interactions via fluoride ions are weaker as compared to oxide ions. 35 In this respect, a comparison of the magnetic properties and structures to the system of the La2NiO4+d is also interesting. In La2NiO4+d, only the stoichiometric samples with d = 0 are reported to possess 3D antiferromagnetic ordering up to temperatures of 300 K 62 , while slightly over-stoichiometric compounds (d > 0) show considerably lower transition temperatures.…”

Synthesis and characterisation of fluorinated epitaxial films of BaFeO2F: tailoring magnetic anisotropyviaa lowering of tetragonal distortion

“…decreasing of the Néel temperatures from 750 K for LaFeO 3 to 645 K for BaFeO 2 F, and even further to ∼480 K for AgFeOF 2 ). 38 …”