Magnetic Structure and Properties of the Rechargeable Battery Insertion Compound Na2FePO4F

Abstract

The magnetic structure and properties of sodium iron fluorophosphate Na2FePO4F (s.g. Pbcn), a cathode material for rechargeable batteries, were studied using magnetometry and neutron powder diffraction. The material, which can be described as quasi-layered structure with zig-zag Fe-octahedral chains, develops long-range antiferromagnetic order below ~3.4 K. The magnetic structure is rationalized as a super-exchange driven ferromagnetic ordering of chains running along the a-axis, coupled antiferromagnetically by super- super-exchange via phosphate groups along the c-axis, with ordering along b-axis likely due to contribution of dipole-dipole interactions.