Small-angle scattering investigations of cobalt-ferrofluids using polarised neutrons

Combining contrast variation using polarised neutrons and various H/D mixtures of solvents allowed different structural units in Co-ferrofluids to be identified by small-angle scattering. In diluted liquids, the magnetic core behaves as a non-interacting single-domain. The core is encapsulated by a shell of surfactant molecules which was found to be impenetrable for the solvent. In more concentrated samples aggregation appears in an external magnetic field which is described by a densely random packing of hard spheres.