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Hitachi Achieves Storage Breakthrough in Areal Density via Perpendicular Recording
In September 2006, Hitachi Global Storage Technologies demonstrated an areal
density of 345 gigabits per square inch (Gbits/sq. in.) on perpendicular
recording technology. This areal density, demonstrated in laboratory testing,
represents an increase of more than two-and-a-half times the areal density of
today's highest-capacity products.
By 2009, Hitachi predicts that 345 Gbits/sq. in. would result in a
two-terabyte (TB) 3.5-inch desktop drive, a 400-gigabyte (GB) 2.5-inch notebook
drive or a 200-GB 1.8-inch drive2 . In the first quarter of 2007, Hitachi
brought hard drive areal density half-way to the 345 Gbits/sq. in. mark with its
new 1-TB 3.5-inch Deskstar 7K1000.
Why Perpendicular Recording is Needed
One of the key challenges facing the hard drive industry is overcoming the
constraints imposed by the super paramagnetic effect, which occurs when the
microscopic magnetic grains on the disk become so tiny that ambient temperature
can reverse their magnetic orientations. The result is that the bit is erased
and thus, data is lost.
Perpendicular Recording Defined
In longitudinal recording, the magnetic
orientation of the data bits is aligned horizontally, as its name indicates,
parallel to the surface of the disk.
By
contrast, in perpendicular recording, the magnetic orientation of the data bits
is aligned vertically, perpendicular to the disk. In this orientation, materials
and smaller crystalline grains can be used wherein it is harder to reverse the
magnetic orientation, resulting in smaller physical bits that are still stable
at room temperature.
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