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Phase transitions in a ferrofluid at magnetic field induced microphase separation

D. Lacoste·T. C. Lubensky
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Abstract

In the presence of a magnetic field applied perpendicular to a thin sample layer, a suspension of magnetic colloidal particles (ferrofluid) can form spatially modulated phases with a characteristic length determined by the competition between dipolar forces and short-range forces opposing density variations. We introduce models for thin-film ferrofluids in which magnetization and particle density are viewed as independent variables and in which the non-magnetic properties of the colloidal particles are described either by a lattice-gas entropy or by the Carnahan-Starling free energy. Our description is particularly well suited to the low-particle density regions studied in many experiments. Within mean-field theory, we find isotropic, hexagonal and stripe phases, separated in general by first-order phase boundaries.

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D. Lacoste, T. C. Lubensky. 2001-03-21. Phase transitions in a ferrofluid at magnetic field induced microphase separation. https://doi.org/10.1103/physreve.64.041506

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