Electron paramagnetic resonance of Fe3+ ions in (NH4)2SbF5

EPR studies of (NH4)2SbF5 single crystals doped with Fe3+ show that iron substitutes for antimony in orthorhombic sites and that the spectra remain the same from 77°K to room temperature. Hyperfine splitting from five nearest neighbor fluorines, four ’’planar’’ and one ’’axial’’, is resolved and suggests that the species observed is FeF52−. It is noted that for general orientations of the applied magnetic field the ligand hyperfine structure differs from one Fe3+ fine structure transition to another so that the iron ions cannot be in the plane of the four ’’planar’’ fluorines of the FeF52− species. The large hyperfine splitting for the axial fluorine suggests that it is closer to the Fe3+ ion than are the planar fluorines. The spin Hamiltonian parameters are g = 1.9956±0.0003, ‖D‖ = 690±28, ‖E‖ = 15.2±1.2, ‖a‖ = 32.8±8 and ‖F‖ = 6±3; the fluorine hyperfine constants are ‖A′‖ = 17±4, ‖B′‖ = 15±4 (planar fluorines) and ‖A″‖ = 69±4, ‖B″‖ = 72±4 (axial fluorine) (values are in units of 10−4 cm−1). The fluorin...