Effects of Cell Confinement on the Evolution of Field-Induced Structures in a Magnetorheological Fluid

The evolution of field-induced structure in ferrofluid emulsions is studied during the "gas-solid" phase transition. The chain formation and coarsening are measured by monitoring the average separation between aggregates d using static light scattering and optical microscopy. A powerlaw relation, d -tr, is obtained for all measured cell thicknesses ranging 10 c L c 700 jim along the field direction. The rate of chain coarsening strongly depends on the chain length, weakly depends on the particle volume fraction and is independent of the field strength at a finite cell thickness. A theoretical model based on thermal fluctuation induced coupling and nucleation theory has been developed to explain the data at large L successfully.