Crossover from mean field to three-dimensional ising critical behavior in a three-component microemulsion system

Critical density fluctuations of water droplets in an oil-rich three-component microemulsion system have been studied by small-angle neutron scattering as a function of temperature near and far from the boundary of phase decomposition. The observed data in the one-phase region are well described in terms of the asymptotic crossover expression calculated by Belyakov et al. The data are found exclusively in the crossover region between the universality class of three-dimensional Ising and mean field regimes. The Ginzburg number is found to be between one and two orders of magnitude less than that for low molecular weight liquids.