  Polar magnetism is present when ions occupy sites that are not centres of
inversion symmetry. Fortunately, such magnetization contributes to neutron
scattering that is the bedrock of magnetic structure determinations.
Experiments in which the scattered neutron polarization is analysed are not a
novelty. Simulations of polarized neutron scattering amplitudes for room
temperature haematite (alpha-Fe2O3) demonstrate the wealth of information on
offer. Two magnetic motifs distinguished by the orientation of their bulk
ferromagnetism are considered. Additionally, the symmetry-inspired simulations
challenge a recent claim to have determined the absolute direction of the
Dzyaloshinskii-Moriya (D-M) interaction.
