Neutron scattering study of the diffuse critical scattering associated with the Verwey transition in magnetite (Fe3O4)

The temperature-dependent diffuse critical scattering associated with the Verwey ordering ($T_V=122\mathrm{}$ K) in magnetite (${\mathrm{Fe}}_3$ ${\mathrm{O}}_4$) is extensively studied by means of neutron scattering experiments. The $q$ dependence of the scattering reveals that it is planar in nature and shown to arise from one-dimensional (1-D) correlations along a cube edge. The diffuse scattering is observable at high temperatures ($T-T_V<100\mathrm{}$ K) and increases rapidly as $T_V$ is approached. Near $T_V$, the spotlike 3-D critical scattering studied by Fujii etal appears. At $T_V$ the diffuse scattering shows an abrupt decrease and is absent below. Inelastic studies show that the diffuse scattering is predominantly inelastic and couples strongly to the transverse acoustic phonons propagating with $q$ in the plane of diffuse scattering. The spectra are interpreted via a pseudospin-phonon theory and the significant parameters are derived.