Structure and dynamics of complex liquids with magnetic dipole-dipole interactions by means of static and dynamic X-ray scattering

Complex liquids consisting of spherical core-shell colloids with a magnetic cobalt ferrite core and a silica shell are studied by means of static small-angle X-ray scattering (SAXS) and X-ray photon correlation spectroscopy (XPCS). In contrast to conventional ferrofluids, these particles exhibit a significantly narrower size distribution and are electrostatically stabilized by charged surface groups of the silica shell. The particles self-organize into crystalline and liquid-like ordered systems, whose structural and dynamic properties are investigated. Due to the competition of the magnetic dipole-dipole interaction with a soft Yukawa potential, these colloidal liquids become anisotropic in the presence of weak magnetic fields, comparable to the earth's magnetic field. (c) 2004 Elsevier B.V. All rights reserved.