Simulation of field-induced structural formation and transition in electromagnetorheological suspensions

A computer simulation method has been used to study the three-dimensional structural formation and transition of electromagnetorheological (EMR) suspensions under compatible electric and magnetic fields. When the fields are applied simultaneously and perpendicularly to each other, the particles rapidly arrange into single layer structures parallel to both fields. In each layer, there is a two-dimensional hexagonal lattice. The single layers then combine together to form thicker sheetlike structures. With the help of the thermal fluctuations, the thicker structures relax into three-dimensional close-packed structures, which may be face-centered cubic (fcc), hexagonal close-packed (hcp) lattices, or, more probably, the mixture of them, depending on the initial configurations and the thermal fluctuations. On the other hand, if the electric field is applied first to induce the body-centered tetragonal (bct) columns in the system, and then the magnetic field is applied in the perpendicular direction, the bct to fcc structure transition is observed in a very short time. Following that, the structure keeps on evolving due to the demagnetization effect and finally forms close-packed structures with fcc and hcp lattice character. The simulation results are in agreement with the theoretical and experimental results.