MAGNETIC-PROPERTIES AND MICROSTRUCTURE OF FE-O AND CO-O THIN-FILMS

Iron oxide and cobalt oxide thin films were prepared by reactive DC ma gnetron sputtering in a mixture of Ar and O-2 gases. The stoichiometry of the oxide films was studied as a function of the amount of O-2 dur ing deposition, Sputtering conditions, including de power and oxygen-t o-argon ratio, were found which allowed pure FeO, Fe3O4, alpha-Fe2O3, CoO, and CO3O4 films to be fabricated. The microstructure of the films , and especially the grain shape and size distribution, were quite dif ferent for oxide films with different stoichiometry, The crystallograp hic axes of Fe-O films were randomly oriented in contrast to Co-O film s in which a strong [111] texture was found, A strong ferromagnetic li ke behavior was observed in FeO and alpha-Fe2O3 films, in contrast to the well-established antiferromagnetic behavior in bulk, The reason fo r this anomalous behavior is attributed to clusters of defects in FeO films and uncompensated surface spins in alpha-Fe2O3 films, A large sh ift (3800 Oe) was observed in the low temperature hysteresis loop of a field cooled sample consisting of 50% Co and 50% CoO. A similar but l ess pronounced effect was observed in FeO and alpha-Fe2O3 films. This result is believed to be caused by a strong exchange coupling between the ferromagnetic and antiferromagnetic constituents in these composit e films.