Chain formation in magnetic fluid composites

The particle structures observed when a magnetic field of 20 Oe is applied to a composite consisting of polystyrene spheres dispersed in a ferrofluid have been compared with predictions given by Monte-Carlo simulations. Very close correspondence between theory and experiment is obtained. Chain lengths have been derived theoretically and experimentally and measured as a function of particle concentration C and diameter D. Empirical relations for the chain length, defined as the average number of particles per chain, give n α c^3/2and n α D²for systems where the concentration c < 0.25.