Dynamics of the field-induced formation of hexagonal zipped-chain superstructures in magnetic colloids

DIRK HEINRICH; ALEJANDRO R. GOÑI; A. SMESSAERT; SABINE H. L. KLAPP; LUCAS M. C. CERIONI; TRISTÁN M. OSÁN; DANIEL J. PUSIOL; CHRISTIAN THOMSEN

PHYSICAL REVIEW LETTERS

AMER PHYSICAL SOC

Año: 2011 vol. 106 p. 2083011 - 2083014

0031-9007

Combining nuclear magnetic resonance and molecular dynamics simulations, we unravel the long-time dynamics of a paradigmatic colloid with strong dipole-dipole interactions. In a homogeneous magnetic field, ionic ferrofluids exhibit a stepwise association process from ensembles of monomers over stringlike chains to bundles of hexagonal zipped-chain patches. We demonstrate that attractive van der Waals interactions due to charge-density fluctuations in the magnetic particles play the key role for the dynamical stabilization of the hexagonal superstructures against thermal dissociation. Our results give insight into the dynamics of self-organization in systems dominated by dipolar interactions.