Magnetic measurements of self-organisation

Self-organisation is an important topic due to its possible use in magnetic recording. In this paper, the mechanism of self-ordering is investigated using non-magnetic polystyrene spheres dispersed in a thin layer of ferrofluid. When a field is applied perpendicular to the plane of the sample, the non-magnetic holes develop a Lorentz cavity field proportional to the magnetisation of the ferrofluid. The containment of the spheres and the dipole-dipole repulsive force between them leads to self-organisation. The degree of order was determined by Fourier analysis. The results show that there is greater ordering of the spheres with larger applied fields, showing that the only factors in the self-ordering are the boundary conditions and a repulsive force. (c) 2004 Elsevier B.V. All rights reserved.