Structure and magnetic properties of the cubic oxide fluoride BaFeO2F

Abstract

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.

Magnetic interactions in cubic-, hexagonal- and trigonal-barium iron oxide fluoride, BaFeO2F

“…BAB ), it is assigned the letter h [16]. For a stapling sequence ccc… the simple cubic perovskite structure is formed as found, for example, in SrFeO 3 whereas the hexagonal perovskite structure is obtained for the Furthermore, the magnetic structures of the hexagonal-and trigonal-modifications of BaFeO 2 F as revealed by neutron powder diffraction are complex [14,15] and, as might be expected, are different from those identified by neutron powder diffraction and 57 Fe Mössbauer spectroscopy in cubic BaFeO 2 F [9]. Cubic BaFeO 2 F shows G-type antiferromagnetic ordering, i. e. each iron atom possesses spin direction opposite to its nearest neighbours.…”

“…We have now recorded 57 Fe Mössbauer spectra from both 6H-BaFeO 2 F and 15R-BaFeO 2 F at temperatures between 630K and 15 K. We report here on these spectra and compare them with data recorded over a similar temperature range from cubic BaFeO 2 F [9]. The results are discussed in terms of the different magnetic interactions between the Fe 3+ ions which originate from the differences in crystal structure.…”

“…It can be seen in Figure 1a that each Fe 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 consist of a single magnetic sextet with broadened lines [9]. The single sextet arises from the single crystallographic site of the Fe ions can lead to a more covalent interaction which will result in the observed smaller values of B hf and for these sextet components.…”

Vanadium Oxyfluoride/Few-Layer Graphene Composite as a High-Performance Cathode Material for Lithium Batteries

“…28 No indication of ordering of those ions (e. g. by the appearance of additional superstructure reflections, further splitting of reflections or significant intensity misfit) was obtained. Disorder of oxide and fluoride ions is a well-known phenomenon observed for many perovskite-type transition metal oxyfluorides [29][30][31][32][33][34][35] which can be derived from a ccp stacking of AX 3 layers. In contrast, ordering of fluoride ions was found for many hexagonal type perovskite compounds [36][37][38][39] .…”

Perovskite-Related Oxide Fluorides: The Use of Mössbauer Spectroscopy in the Investigation of Magnetic Properties

“…[12,13] The magnetic properties were found to be substantially different from the related compound SrFeO2F (see above). Mössbauer spectra collected between 400 and 650 K showed decreasing magnitudes of magnetic hyperfine field with increasing temperature and from the variation of the average magnetic hyperfine field with increasing temperature ( Figure 5) a magnetic ordering temperature of ca.…”