Perovskite-related strontium orthoferrite, SrFeO3−δ, has been fluorinated by a low temperature reaction with poly(vinylidene fluoride) to give the compound SrFeO2F. X-ray powder diffraction shows that fluorination leads to an expansion of the unit cell which is consistent with partial replacement of oxygen by fluorine and consequent reduction in the oxidation state of iron. Magnetometry experiments in the temperature range 10–400 K showed small aligned moments (0.003 ± 0.000 05 μB per Fe3+ ion at 2 T and 300 K), indicating the absence of ferro- or ferrimagnetism. The 57Fe Mössbauer spectra recorded at temperatures below about 300 K show broadened, but unsplit, sextet patterns whilst spectra recorded above this temperature show clear splitting of the sextet structure and a magnetic ordering temperature of 685 ± 5 K. A model related to the pattern of substitution by fluorine on the octahedral arrangement of oxygen sites around iron is proposed in which SrFeO2F undergoes a magnetic transition at about 300 K from a low temperature state with random spin directions to an antiferromagnetic state.

Fluorination of the parent oxide, BaFeO 3-δ, with polyvinylidine fluoride gives rise to a cubic compound with a = 4.0603(4) Å at 298K. 57 Fe Mössbauer spectra confirmed that all the iron is present as Fe 3+. Neutron diffraction data showed complete occupancy of the anion sites indicating a composition BaFeO 2 F, with a large displacement of the Fe offsite. The magnetic ordering temperature was determined as T N = 645±5K. Neutron diffraction data at 4.2K established G-type anti-ferromagnetism with a magnetic moment per Fe 3+ ion of 3.95µ B . However, magnetisation measurements indicated the presence of a weak ferromagnetic moment, which is assigned to the canting of the antiferromagnetic structure. 57 Fe Mössbauer spectra in the temperature range 10 to 300K were fitted with a model of fluoride ion distribution that retains charge neutrality of the unit perovskite cell.

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