Polydispersity influence upon magnetic properties of aggregated ferrofluids

In the present paper we compare the static magnetic properties of a bidisperse ferrofluid obtained via computer simulations with the predictions of the theoretical chain model. At weak fields, the computer simulations showed a strong dependence of the magnetization on the concentration of large particles. When the latter is small the magnetization behavior is close to the one given by the modified mean field approach, but at higher concentrations of large particles the initial susceptibility increases significantly. This increase cannot be described in terms of the modified mean field model for the homogeneous system. A new theoretical approach for the description of the static magnetic properties of a bidisperse ferrofluid was developed. The theoretical predictions are in good agreement with the results of a recent computer simulation study.