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Fujitsu HDD Technology Surpasses 100 Gbits/Inch2

At last, the areal recording density of a hard disk drive (HDD) has broken the 100 Gbits/inch 2 barrier. The firm responsible for achieving this long-held objective is Fujitsu Laboratories, Ltd of Japan, which reported successful record and play at an areal recording density of 106.4 Gbits/inch 2 at The Magnetic Recording Conference (TMRC), held in August 2001.

This is about three times the density of other products. The roadmaps of major HDD manufacturers show that they expect products of this level from the end of 2002 through 2003. Given Fujitsu Laboratories’ announcement, it seems that development is running close to schedule. Fujitsu Ltd of Japan, for example, plans to commercialize products of this level in the first half of 2003, probably with a 2.5-inch HDD offering about 55 Gbytes per platter capacity.

Evolving Technology

Fujitsu Laboratories has improved on current technology in their demonstration experiments (see Table). The research team used the Synthetic Ferri (SF) recording medium, originally announced in their April 2000 report on 56.1-Gbit/inch 2 experimentation. The read head used was a double-specular spin-valve head, which had also previously been presented at a society meeting in January 2001. Both areas have been improved without making fundamental changes.

As the team has extended technologies that were already in use, it is likely that they can be commercialized relatively smoothly, and can provide a high standard of reliability. SFMedia overcomes the disadvantage of longitudinal recording media in thermal fluctuation, which is particularly welcome news to HDD manufacturers, as it means they won’t have to introduce an entirely new technology, such as perpendicular magnetic recording.

SFMedia has already begun to enter commercial use: IBM Corp of the US has adopted a recording medium very similar to SFMedia for its 2.5-inch HDD already in volume production, while Fujitsu plans to use it in products from March 2002.

Multi-Gigabit Heads

Fujitsu Laboratories seems to have boosted the limits of longitudinal recording to somewhere up to 300 Gbits/inch 2 , from somewhere between 40 and 100 Gbits/inch 2 . The previous limit was not enough to achieve recording densities of hundreds of Gbits/inch 2 . Even though SFMedia avoids the issue of the thermal fluctuation, it is likely that the read head output will be insufficient. The firm believes that, even with additional improvements to spin-valve heads, a new limit will appear between about 120 and 150 Gbits/inch 2 .

One potential candidate for a head technology to achieve hundreds of Gbits/inch 2 is already in sight. Research results for current perpendicular to plane (CPP) spin-valve heads, where current flows perpendicular to the giant magnetoresistive (GMR) head, were presented by Fujitsu Laboratories, Toshiba Corp of Japan and others at TMRC. TDK Corp of Japan and others, however, are pushing tunneling magnetoresistive (TMR) heads. While both technologies have the potential to break the 100-Gbits/inch 2 barrier, there have so far been no demonstrations. It is likely to take a little longer for the shape of the next big head technology to become apparent.

by Chikashi Horikiri

(November 2001 Issue, Nikkei Electronics Asia)

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