IONIC FERROFLUIDS - INTRAPARTICLE AND INTERPARTICLE CORRELATIONS FROM SMALL-ANGLE NEUTRON-SCATTERING

Ferrofluids are colloidal solutions of subdomain magnetic grains dispersed in a fluid carrier. Chemically synthesized ionic ferrofluids are stabilized in aqueous media through electrostatic charges at the surface of the particles. Like binary mixtures of polymeric solutions, ferrofluids may undergo a phase separation in two coexisting liquids. We explore here the monophasic area of the phase diagram using small-angle neutron scattering from solutions of gamma-Fe2O3 particles of typical size 80 angstrom in the scattering vector q range from 7 x 10(-3) to 1.3 x 10(-1) angstrom-1. In zero magnetic field the isolated particle behaviour is separated from the interparticle structure factor, which varies with the volume fraction up to 8% of magnetic particles.