NEUTRON DIFFRACTION TOPOGRAPHIC INVESTIGATIONS OF “EXOTIC” MAGNETICDOMAINS

Neutron diffraction topography provides unique possibilities for the direct observation and characterization of magnetic domains of various kinds in single crystals. The magnetic contribution to the scattering amplitude can lead to different intensities being diffracted, on a given Bragg peak, by the different domains, hence to area contrast on the topographs. Over the last few years some experience has been gained on the behaviour of the magnetic domains in colinear and helical antiferromagnets. While some (domains in NiO and in Cr) can be imaged indirectly by other methods, they can only be imaged in a direct way using neutron topography, and most of them cannot be observed by any other technique (180° domains in MnF2, CoF2 and α-Fe2O3, chirality domains in helimagnetic Tb, Ho and MnP). A few conclusions on shapes, volume and reproducibility (“memory effect”) of these domains were drawn from the results, and are discussed.