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

• Published in: Physical review letters Vol. 106; no. 20; p. 208301
• Main Authors: Heinrich, D, Goñi, A R, Smessaert, A, Klapp, S H L, Cerioni, L M C, Osán, T M, Pusiol, D J, Thomsen, C
• Format: Journal Article
• Language: English
• Published: United States 20-05-2011
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/physrevlett.106.208301

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.