Small-angle neutron scattering in structure research of magnetic fluids

A magnetic fluid (MF) is a liquid dispersion of magnetic nanoparticies coated by surfactants for stabilization. The MF research reviewed in this paper investigates the atomic and magnetic structure of MF particles and the way they interact depending on conditions by small-angle neutron scattering (SANS). The presence of a liquid carrier in the structure and magnetic properties of MFs, which are very close to those of an ideal superparamagnetic system, allow for the effective use of the major neutron scattering features: the strong effect of hydrogen-deuterium isotopic substitution and magnetic scattering. Аn extension of the contrast variation technique to the structure research on polydisperse and superparamagnetic systems is proposed. The cases of noninteracting and interacting particles, the latter with allowance for cluster formation, are considered for nonmagnetized and magnetized MFs. The polarized neutron scattering analysis of the structure of magnetized MFs is illustrated by examples. Topical problems in further developing the method to study multiparameter systems are identified.