2-BEAM AND 3-BEAM X-RAY-DIFFRACTION IMAGING OF DOMAINS IN MAGNETITE

The X-ray diffraction topographic imaging process for ferrimagnetic do mains in magnetite Fe3O4 at room temperature is investigated, in two- and three-beam cases, for incident synchrotron radiation beams differi ng in angular divergence and energy spread. In the usual two-beam conf iguration, domain or wall contrast is obtained from the difference in Bragg conditions, or from the slight difference in the direction of th e beams diffracted by neighbouring domains, revealed by the large crys tal-to-film distance that can be used at a third-generation synchrotro n radiation facility. A three-beam Umweganregung case involving the we ak 171 and the strong 131 reflections shows unusual domain contrast on the 171 topographs, even on images involving energy or angle integrat ion; this contrast is particularly evident on white-beam topographs. T he high angular sensitivity this implies is associated with the differ ence in dispersion relation between the two reflections.