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Abstract:
We study the equilibrium structure of large but finite aggregates of magnetic dipoles,
representing a colloidal suspension of magnetite particles in a ferrofluid. With increasing
system size, the structural motif evolves from chains and rings to multi-chain and multi-ring
assemblies. Very large systems form single- and multi-wall coils, tubes and scrolls. These
structural changes result from a competition between various energy terms, which can be
approximated analytically within a continuum model. We also study the effect of external
parameters such as magnetic field on the relative stability of these structures. Our results may
give insight into experimental data obtained during solidification of ferrofluid aggregates at
temperatures where thermal fluctuations become negligible in comparison to inter-particle
interactions. These data may also help to experimentally control the aggregation of magnetic
particles.
