2-DIMENSIONAL MAGNETIC LIQUID FROTH - COARSENING AND TOPOLOGICAL CORRELATIONS

We present an experimental study of a cellular system which may be for med in a two-dimensional (2D) layer made of an immiscible mixture of a magnetic fluid and an oil. We obtain a wet or a dry 2D froth, the cha racteristics of which are determined by the strength of an externally applied magnetic field. The froth is formed In an equilibrium state; t he topological and geometrical features of the froth are fixed by the value of the applied field. The cellular pattern of the froth is stabl e in time, and a coarseninglike behavior is observed on decreasing the amplitude of the field. This cellular system can be used as a model t o study topological processes in the equilibrium state, contrary to so ap froths which are nonequilibrium systems because gas diffusion occur s. We show that the topological characteristics are statistically reve rsible after a magnetic-field cycle, and we present a statistical stud y of the froth features as a function of the amplitude of the field. T he topological correlations between neighboring cells are well describ ed by the Aboav-Weaire law. Finally, we consider the area of an n-side d cell, and show that its growth rate (magnetic field dependent) is, i n a surprising manner, proportional to n - 6, similarly to the Von Neu mann law.