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.