New ways of using an old method: some recent applications of polarised neutron diffraction

The polarised neutron diffraction technique, is a well-established tool that has been applied to a wide range of problems. One of the attractions of the method is the relatively straightforward way in which the results can be interpreted in terms of magnetisation distributions. There are however circumstances in which the simple analysis is inappropriate. Examples are given here of some recent applications which exploit lesser known aspects of the technique, and address problems that may be encountered in interpreting the data. In several recent applications changes that take place with temperature, possibly across a phase transition, have been studied. When the proposed mechanism predicates a particular change in the magnetisation distribution the experiments can serve to validate the theory. Methods have been developed to address problems arising from twinning at the transition in both CMR and martensitic materials. The azimuthal angle, which can be varied when using normal beam geometry, provides a means of studying non-collinear magnetisation distributions. The orbital contributions to magnetic scattering from 3d transition metals have been re-examined using this technique.