Two-dimensional concentration domain patterns in magnetic suspensions: Energetical and kinetic approach.

The patterns formed in flat layers of magnetic suspensions and emulsions due to the competing short-range attractions and long-range magnetic repulsion forces are considered. On the basis of calculating energy of the ordered hexagonal and stripe structures of the liquid magnetics it was shown that the stripe phase is energetically preferred at the symmetrical distribution of the particles between concentrated and diluted phases. If one phase prevails the formation of the array of the separate droplets is expected. Results of the numerical calculation of the energies of the stripe and hexagonal patterns are confirmed by the numerical simulation results of the kinetics of the magnetic field induced phase separation. Numerical simulation by the pseudospectral technique of the dynamics of the concentration perturbation show that at nonsymmetrical distribution of the particles between phases the periodic array of the separated droplets arises. Long-range magnetic repulsion forces are crucial for the formation of ordered arrays of the stripes or droplets since if they are absent characteristic coarsening phenomena at late stages of the phase separation are observed. [ABSTRACT FROM AUTHOR]