||Fujitsu Laboratories Ltd.
Fujitsu Develops HDD Read-Head Technology for 300Gb/in2 Densities
Tokyo, May 15, 2002 -- Fujitsu Laboratories Ltd. today announced
the development of an advanced giant magneto-resistive (GMR) head
for reading data on hard disk drives with recording densities of
300 gigabits per square inch (Gb/in2) and greater. This ground-
breaking technology will enable individual 2.5" hard-drive units
to have capacities in the range of 160 to 360 gigabytes (GB),
with commercial introduction of the new read-head technology
expected within two to four years.
Details on Fujitsu's breakthrough technology were presented on
May 2 at Intermag Europe 2002 in Amsterdam.
Existing GMR read heads used in hard drives operate the Current-
in-Plane (CIP) mode, in which electric current flows in parallel
with the GMR element's membrane. In this mode, the greater the
recording density, the smaller the size of read element,
resulting in reduced output of playback signal. Accordingly,
the practical limit for recording densities using this mode is
believed to be around 100Gb/in2.
To get around this constraint, focus has shifted to the
development of Current-Perpendicular-to-Plane (CPP) mode heads,
which can be either GMR or Tunnel Magneto-Resistive (TMR) heads.
TMR heads have a high signal output, but it is difficult to
lower resistance, which limits element miniaturization and speed
of operation. CPP-GMR heads developed to date, on the other
hand, consist of four layers (a free layer, pin layer,
non-magnetic intermediate layer, and an anti-ferromagnetic
layer), all of which are metallic, thereby reducing resistance
when current runs perpendicular to the element. This
facilitates miniaturization and high speed operation, however,
playback signal output is reduced due to smaller fluctuations
in element resistance.
In Fujitsu's newly developed CPP-GMR head, the GMR element's
membrane includes an extremely thin partially oxidized magnetic
layer, mere nanometers thick, enabling the CPP-GMR head to
control the flow of current in the GMR element while raising the
resistance fluctuation to practical levels. Researchers were
able to raise the magnetic resistance fluctuation ratio to 5.0%,
eight times the level of previously developed CPP-GMR elements,
and element resistance fluctuations were increased approximately
60 times. As a result, ample playback signal output would be
possible even at densities of 150-300Gb/in2. Compared to TMR
elements, the new CPP-GMR element has only one-tenth the element
resistance, so that even at small sizes, increases in head
resistance are limited, making high-speed data transfers possible.
The following table shows a comparison of new and the previously
developed CPP-GMR elements.
|Element resistance RA|
|Element resistance fluctuations ΔRA|
|Magnetic resistance fluctuations ratio (%)||5.0||0.61
Fujitsu is actively working to incorporate this technology in
read heads for hard drives with recording densities of 150-300Gb/in2.
[About Fujitsu Laboratories Ltd.]
Founded in 1968 as a wholly owned subsidiary of Fujitsu Limited,
Fujitsu Laboratories Limited is one of the premier research
centers in the world. With a global network of laboratories in
Japan, China, the United States and Europe, the organization
conducts a wide range of basic and applied research in the areas
of IT Core Systems, IT Media, Networks, Peripherals, Advanced
Materials and Electronic Devices.
Minoru Sekiguchi, Scott Ikeda
Fujitsu Limited, Public & Investor Relations
Tel: +81-3-3215-5259 (Tokyo)
Fujitsu Laboratories Ltd.
Advanced Magnetic Recording Research Div.
Tel: +81-46-250-8832 (Atsugi)
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