Particle pair correlation in a magnetically saturated ferrofluid

The field dependence of particle pair correlations in a ferrofluid is investigated using MC simulation and integral equation techniques. In order to simplify calculations a system is chosen where the magnetic field is sufficiently large that thermal fluctuations of the magnetisation of the individual particles can be ignored. The MC calculations were performed using standard techniques for a three dimensional model of a ferrofluid where the particles are assumed to interact via a spherical hard core plus a short range interaction due to the entropic repulsive forces provided by the surfactant molecules and a long range potential assumed to be produced by a point dipole embedded in the particle centres. The results are compared with those obtained using the hypernetted chain approximation by expanding the pair correlation function in terms of Legendre polynomials with respect to angle to the external field. Very good agreement is found between the two methods enabling accurate and smooth correlation functions to be obtained for large external fields at densities typical of ferrofluids.