Local bonds anomalies and dynamics in bismuth ferrite

The temperature evolution of the chemical and magnetic sublattice of bismuth ferrite has been investigated by neutron scattering below room temperature. Although the bulk lattice structure performed as expected, anomalies were measured in the local Bi-Fe and Fe-O bond lengths around 205 K, distorting the Fe polyhedra. The intensity and width of magnetic Bragg reflections were observed not to monotonically decrease as the system cooled, with distinct anomalies at 205 K. Inelastic neutron scattering above and below the 205 K transition revealed no significant difference in the low energy acoustic phonon. These insights will underpin and stimulate more detailed work aimed at understanding further the bismuth ferrite ordering taking place around 205 K.