Magnetization of ferrofluids with dipolar interactions - a Born--Mayer expansion

For ferrofluids that are described by a system of hard spheres interacting via dipolar forces we evaluate the magnetization as a function of the internal magnetic field with a Born--Mayer technique and an expansion in the dipolar coupling strength. Two different approximations are presented for the magnetization considering different contributions to a series expansion in terms of the volume fraction of the particles and the dipolar coupling strength.Comment: 19 pages, 11 figures submitted to PR

Domain structures in thin layers of a ferrocolloid

We consider the problem of formation of structures composed of identical domains in a ferrocolloid that fills a space between two closely situated parallel planes under action of a normal external magnetic field. Those structures begin to arise under conditions favouring the phase separation of the ferrocolloid. An inhomogeneous system including two equivalent colloidal phases would ultimately evolve due to Ostwald ripening, but for a scaling effect of the planes that stops the evolution at a certain level and makes for the resulting domain structure being stable. A method to find out main characteristics of the domains, such as their size and concentration, is developed for both chaotic and regular (ordered) structures