Etude cristallographique et par effet Mössbauer du fluorure ferrimagnétique Na5Fe3F14γ

The structure of ferrimagnetic γ-Na₅Fe₃F₁₄ has been determined by single-crystal X-ray diffraction. The cell is tetragonal with space group P4₂2₁2 and parameters a = 7.345 ± 0.007 Å and c = 10.400 ± 0.007 Å. The iron atoms occupy a twofold and a fourfold position in the lattice and are octahedrally surrounded by fluorines. These octahedra share corners and form two-dimensional layers of formula (Fe₃F₁₄)^5n?_n. The Mössbauer spectra were measured from 4.2 to 293°K and the results are discussed in terms of the position and environment of iron atoms in the lattice.