Behaviour of materials in magnetic fields studied by small-angle X-ray scattering

Traditionally the combination of electromagnetic fields and small-angle X-ray scattering has been mainly employed in the study of liquid crystals. However, with stronger magnetic fields becoming available owing to developments in superconductor technology it is possible to access a domain where larger macromolecular materials show, in some cases, a susceptibility to magnetic fields due to diamagnetic interactions. This effect can be used in several ways. The most obvious one is to use the alignment of the molecules to perform fibre diffraction experiments. Using an on-line split coil super-conducting magnet it is also possible to perform time-resolved studies on the re-orientation of, for instance, smectic liquid crystals under the influence of changing fields. In experiments where one is interested in the fundamental physics of liquid-crystal displays the use of magnetic fields often is preferred over the use of electric fields since there are fewer problems with ionic sample contaminations and temperature dependent susceptibilities.