Ferrofluid monolayers: monodisperse particles

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Non Branched systems

We investigate the peculiarities brought by the Quasi-2D geometry into the aggregation ferrofluid microstructure in particular in the range of parameters for which the chain-like structures have been observed implicitly or explicitly in 3D experiments, simulations and theoretical models. In difference to previous papers studying aggregates in q2D monolayers, we focus our attention on the detailed analysis and extensive comparison of the results coming from MD simulations with a newly developed theoretical approach, which give us cluster sizes and distributions as functions of the magnetic interaction and area fraction of ferroparticles in monolayers.

A thorough comparison of the predictions of the theory with the values obtained through equilibrium Molecular Dynamic simulations have shown that: in the range of the space of parameters  \lambda (dipolar coupling), and area fraction  \phi in which the theory could be expected to be valid (regions with low number of branched structures), the theory is able to closely predict the simulation results, and allow us to calculate the partition functions for these clusters in constrained geometries and describe the influence of the latter constraints on the entropy of a ferrofluid.

The comparison shows that excluded area interactions play a crucial role in quasi 2D, where the constrains imposed by the Q2D monolayer geometry change the entropy of clusters. The refinement of the present theory by dropping out several of the limiting constraints is currently being worked out.

Branched and Network systems

At high values of the dipolar coupling and area fraction parameters, the systems exhibit kind of network and branched structures which are currently characterized via simulation and theory.