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October 16, 2007

Hitachi Helps the Incredible Shrinking Hard Disk Get Even Smaller

By Mae Kowalke, TMCnet Associate Editor

Apple (News - Alert), Inc. may be betting on Flash solid state media as the portable storage format of the future, but Hitachi for one isn’t ready to give up on traditional hard disk technology just yet. Hitachi (News - Alert) Global Storage Technologies and Hitachi, Ltd. on Monday unveiled what they describe as the world’s smallest read-head technology for hard disk drives.

The new technology is expected to increase the storage capacity of hard disks to four terabytes for a desktop computer and one terabyte for a laptop. This gain was achieved by reducing the size of recording heads by more than a factor of two, with the result being heads in the 30-50 nm size range (that’s as much as 2,000 times smaller than the width of an average human hair, Hitachi said).
Hitachi said it expect the new technology will be shipped in products sometime during 2009, and will reach its full potential by 2011.
Hiroaki Odawara, research director at the central lab of Hitachi’s storage technology research center, said the company continues to invest in research that advances the functionality of hard disks—and that, at least for the foreseeable future, no other technology will be able to beat the hard disk’s combo of high capacity and low price.
“This is an achievement for consumers as much as it is for Hitachi,” Odawara said in a statement. “It allows Hitachi to fuel the growth of the ‘Terabyte Era’ of storage, which we started, and gives consumers virtually limitless ability for storing their digital content.”
In its announcement, Hitachi explained that the continual demand for smaller and smaller hard drives has tested the limits of the technology’s capabilities, since electrical resistance increases as the heads shrink, creating more noise output and interfering with the head’s ability to read data. Since high signal output and low noise is what researchers strive for, achieving a high signal-to-noise (S/N) ratio is key to effective read-head technology.
Traditionally, Hitachi further explained, hard disks were developed using a tunnel magneto-resistance, or TMR head—“composed of a three layer structure of an insulating film sandwiched between ferromagnetic films.” TMR heads are limited in that, once recording densities exceed 500 Gb/in, read accuracy become unreliable.
To make shrink the hard drive beyond those boundaries, Hitachi used an alternate type of head referred to as CPP-GMR, which works reliably in very small dimensions. The company still had to overcome previous limitation of CPP-GMR, though, relating to boosting the S/N ratio.
“A high electron-spin-scattering magnetic film material was used in the CPP-GMR layer to increase the signal output from the head, and new technology for damage-free fine patterning and noise suppression were developed,” Hitachi said in its announcement. “As a result, the signal-to-noise ratio, an important factor in determining the performance of a head, was drastically improved.”
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Mae Kowalke previously wrote for Cleveland Magazine in Ohio and The Burlington Free Press in Vermont. To see more of her articles, please visit Mae Kowalke’s columnist page. Also check out her Wireless Mobility blog.

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