LAUSR

We investigate by Monte Carlo simulation how the ferromagnetic ordering transition in a polar fluid is affected by the addition of nonpolar particles. To this end, we consider a mixture of dipolar and pure hard spheres of equal size. Using simulations in the Gibbs ensemble, we first determine the demixing domain in the region of high densities and mole fractions of the polar particles. Then, starting from a purely dipolar fluid at two different densities and monitoring the variation of the order parameter, it is shown that the addition of hard particles favours the alignment of the dipoles. The critical temperature of the transition is finally determined and we show how it is modified, depending on the vicinity of the demixing transition. The interplay of the orientational transition and the demixing transition is finally discussed. GRAPHICAL ABSTRACT