Two- and Three-Beam X-ray Diffraction Imaging of Domains in Magnetite

The X-ray diffraction topographic imaging process for ferrimagnetic domains in magnetite Fe₃O₄ at room temperature is investigated, in two- and three-beam cases, for incident synchrotron radiation beams differing in angular divergence and energy spread. In the usual two-beam configuration, domain or wall contrast is obtained from the difference in Bragg conditions, or from the slight difference in the direction of the beams diffracted by neighbouring domains, revealed by the large crystal-to-film distance that can be used at a third-generation synchrotron radiation facility. A three-beam Umweganregung case involving the weak 171 and the strong 131 reflections shows unusual domain contrast on the 171 topographs, even on images involving energy or angle integration; this contrast is particularly evident on white-beam topographs. The high angular sensitivity this implies is associated with the difference in dispersion relation between the two reflections.