of progress has been made in the development of In the last twenty years a great amount new magnetic materials. Permanent magnets have progressed from the AlNiCo's (with (BH)m-8 MGOe) to the strong rare-earth magnets of SmCo "BH)m-20 MGOe), Sm2(Co,Fe,Cu,Zrh7 s "BH)m-30 MGOe) and the recently discovered Nd-Fe-B super-magnets with (BH)m-50 MGOe. For years the magnetic storage industry has employed Fe0 and CrO for storage media and 2 3 z permalloys and ferrites for recording heads. The recent development of thin film heads, the demand of higher density of information storage and the emergence of completely new technologies, like magneto-optics, call for entirely new types of magnetic materials. Another area in which new techniques of materials preparation have made a dramatic impact is the epitaxial growth of magnetic films. Recent work has shown that this process can be controlled on the scale of atomic monolayers permitting the growth of totally artificial structures, such as artificial superlattices with a resolution on this scale. Epitaxial growth has also permitted the stabilization of metastable phases in thin film form.
These new phases often possess striking properties, such as strong perpendicular anisotropies, which may prove useful for technological applications such as recording. Research on magnetic multilayers and superlattices is increasing at an accelerating pace. Complex couplings between different magnetic layers lead to new properties not seen in bulk materials.