The preparation of ordered colloidal magnetic particles by magnetophoretic deposition

The preparation of ordered two-dimensional (2D) magnetic nanoparticles using a magnetophoretic technique is reported. The quality of the ordering can be observed by electron microscopy and the lattice constants determined by electron diffraction. Using image processing it can be shown that the cobalt particles condense into a hexagonal close packed array, and that the crystallographic axes of the individual cobalt particles are randomly oriented. Furthermore, the equilibrium distance between the 2D ordered particles decreases with increasing strength of the magnetic field while the minimum distance corresponds approximately to the size of the adsorbed stabilizers. The method is of general interest as a means of preparing monolayer films of nanosized magnetic particles such as cobalt or iron oxide.