Hitachi reckons it has kicked the feared super-paramagnetic effect a decade into the future, by demonstrating the disk industry's highest magnetic recording density yet - 230 Gb per square inch, or 356 Mb per square mm. The demo used perpendicular recording technology, and Hitachi Global Storage Technology (HGST) said it could lead to 20GB one-inch Microdrives in two years time, compared to 6GB today.
The big challenge is how to shrink the magnetised grains in the media, said John Best, HGST's chief technologist. The problem is if they get too small, they affect each other too much, plus the energy in each bit gets close to the background thermal energy of the platter - hence the super-paramagnetic effect. The limit is therefore in sight for longitudinal recording, which stripes bits over the magnetic surface and currently peaks at around 100 Gb per square inch.
Best said perpendicular recording has several advantages. One is simple - bits take up less space standing on end than they do lying on their backs. But there are others too: the recording field goes through the medium perpendicularly, so it can be more finely focused. Plus, a soft magnetic underlayer picks up the write field and acts as a second pole, approximately doubling the write power and allowing more resilient magnetic alloys to be used.
"This set of things is worth at least two or three times today's recording densities," said Best. "Then perpendicular can be scaled, for example by tilting the media or applying patterning, to eventually reach 10 times the density. Each new generation takes significant invention, but now we have the potential to get beyond a Terabit per square inch - that's good for ten years."
Hitachi is not the first to demonstrate perpendicular recording though - Seagate used it to demo 100 Gb per square inch back in 2002, and last year Toshiba said it would be the first to commercialise the technology, using it to design an 80GB 1.8 inch drive.
The Toshiba drives are 133Gb per square inch and 40GB per platter, and a spokesman said they will be in mass production by June this year.
Best said that Hitachi is testing perpendicular recording in 2.5 inch laptop drives now, and will have products for sale by the end of this year. These won't be 230 Gb per square inch though - that's only in the lab. Still, a 2.5 inch drive using perpendicular recording to achieve 120 or 130 Gb per square inch could offer 75GB per platter - some 50 percent more than today's longitudinal recording equivalents. ®