Magnetic Structure and Properties of the Li-Ion Battery Materials FeSO4F and LiFeSO4F
Résumé
Using magnetic susceptibility and low-temperature neutron diffraction experiments we present a thorough characterization of the magnetic properties of LiFeSO4F and FeSO4F. Temperature dependent magnetic susceptibility measurements show a transition to long-range antiferromagnetic order at 100 K in FeSO4F whereas the ordering temperature in LiFeSO4F is 25 K. We attribute the decreased ordering temperature to a structural change which decreases the strength of the magnetic interactions along the length of the chains and to the difference of supersuper- exchange interactions between Fe2þ and Fe3þ ions. Powder neutron diffraction experiments were used to determine the magnetic structures of both compounds, which are discussed in terms of exchange interactions and the anisotropy of Fe2þ. The iron magnetic moments are antiparallel within the chains, whereas the coupling between the chains is different in the lithiated compound compared to the delithiated one, resulting in different spin arrangements