DETERMINATION OF STRUCTURES IN FERROFLUIDS BY SMALL-ANGLE NEUTRON-SCATTERING

Stable colloidal dispersions of magnetic particles, or ferrofluids, form a technologically important class of magnetic fluids with novel structural features at the microscopic level. Small-angle neutron scattering (SANS) has proved to be ideally suited to the study of such structures. In addition to the techniques of neutron refractive index variation which have made SANS a tool of choice for studying colloids in general, the uniquely powerful methods of neutron polarisation analysis may be applied to ferrofluids, providing a selection rule for studying non-magnetic and magnetic structural features separately. This article considers the application of SANS to studies of dilute ferrofluids, after which extension of the techniques to concentrated (interacting) dispersions will be addressed. Advances in understanding binary colloidal mixtures in which at least one component is magnetic will then be considered. Finally, the use of ferrodispersion to generate ordered colloidal structures in ferrofluids will be discussed.