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Fujitsu Develops HDD Read-Head Technology for 300Gb/in2 Densities
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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.

[New Technology]
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.

Previous CPP-GMR
Element resistance RA
Element resistance fluctuations ΔRA
Magnetic resistance fluctuations ratio (%)5.00.61

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.

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[Press Contacts]
Minoru Sekiguchi, Scott Ikeda
Fujitsu Limited, Public & Investor Relations
Tel: +81-3-3215-5259 (Tokyo)
Fax: +81-3-3216-9365
Mail Press Inquiries
[Technical Contact]
Atsushi Tanaka
Fujitsu Laboratories Ltd.
Advanced Magnetic Recording Research Div.
Tel: +81-46-250-8832 (Atsugi)
Fax: +81-46-250-8178

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