Magnetic properties of ferrofluids: an influence of chain aggregates

The paper is devoted to the basic problem of chain aggregate structure in magnetic fluids under the influence of an external magnetic field. A traditional free-energy density functional approach is used, and the chain partition function of a flexible chain is calculated under the condition when both the interparticle dipole-dipole interaction between the nearest neighboring ferroparticles in a chain and the interaction of particle magnetic moments with an external field are taken into account with the help of rotational matrix techniques.