Monte-Carlo simulations of light transmission in dispersions of paramagnetic particles

Calculations were made of pair correlation functions in dispersions of interacting paramagnetic particles, as a function of applied magnetic field. Calculations were also made of light transmission through the colloid, which included a geometric shadowing effect and also took account of interference effects between the particles by effective extinction cross-section dependent on the microscopic structure. This, coupled with an effective number density determined by the geometric shadowing effects were used to calculate light transmission curves. These show minima and maxima consistent with experimental data. These data were incompatible with a simple model based on geometrical shadowing alone, which gave a monotonic increase of transmission with applied magnetic field.