Aggregation in ferrofluids studied by Neutron Small Angle Scattering

Abstract

Neutron Small Angle Scattering has been used to follow processes of particle aggregation in ferrofluids under various conditions of temperature and externally applied magnetic field. Cobalt particles, stabilized in toluene by one of two surfactant materials, showed neutron scattering characteristic of highly aggregated systems. Low temperature quenching in a strong magnetic field caused physical shape anisotropy to be fixed in the samples. A smaller particle system revealed no magnetic anisotropy after removal of the magnetic field whereas the larger particle system did retain anisotropic magnetic characteristics while held in the solid state