Today,
our Travelstar drives have areal densities
which are up to thirty-four gigabits per
square inch (Travelstar 40GN). If conventional
disk media were used at this areal density,
the effects of superparamagnetism could
reduce thermal stability of magnetically
stored information. To delay this effect,
AFC media was introduced into Travelstar
30GN series of disk drive products, the
first in the industry, and has continued
the application of this technology in the
latest Travelstar 60 GH, 40 GN mobile drives.
In addition, Hitachi has introduced AFC
media into the desktop disk drive market
with the Deskstar 120 GXP, another industry
first. hitachi has pioneered the use of
exchange coupled structures and materials
which are also used in today's GMR heads.The
new media structure consists of two magnetic
layers separated by a thin, 6 C, film of
the element ruthenium which produces an
antiferromagnetic coupling of top and bottom
magnetic layers. This ruthenium film is
only about 3 atom layers in thickness permitting
the effective magnetic thickness, Mrt, of
this entire structure to be the difference
between top and bottom magnetic films, therefore
independent of actual individual layer thickness.
Both magnetic layers can now be thicker
at higher areal densities allowing larger
diameter alloy grains which are more thermally
stable. AFC media is expected to extend
areal density growth to 100 Gbits/in2 and
beyond, while maintaining good thermal stability
of the recorded information.
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