Magnetic domain studies of cobalt nanostructures

The pulsed laser deposition technique associated with a low energy cluster beam is used to deposit cobalt thin films with a thickness 100-200 nm and cobalt dots of a diameter 100-200 nm on silicon substrates. The deposited thin films of Co are composed of clusters of a size 10- 50 nm, with very few large grains as revealed by atomic force microscopy. The observations performed by magnetic force microscopy on as-grown thin films reveal randomly distributed out-of-plane magnetic domain structures. These magnetic domains are aligned linearly by applying an external magnetic field either perpendicular or parallel to the substrate during the deposition. In addition, the effect of film thickness and roughness on multidomains is reported. The increase of roughness resulted in the decrease of magnetic domain width from 200 to 100 nm. This decrease is accompanied by the appearance of instability in the stripe domain pattern. Well separated cobalt dots of diameter in the range of 100-200 nm are also deposited on silicon substrates, which show arc-like multidomains. The domains seem to be oriented along the long axis of the dots. The domain structure of Co nanodots is similar to that of Co thin films indicating strong magnetic coupling of clusters.