IBM boffins have unlocked a way of quadrupling data density on hard disk drives. The technology is called "antiferromagnetically-coupled (AFC) media,"; it's pretty damn clever, and the first product incorporating AFC ships in volume today.

By sandwiching a "three-atom-thick layer of the element ruthenium", between two magnetic layers, IBM researchers have overcome the biggest barrier to increasing density on hard drives, which until today, was approaching the practical maximum density.

"When magnetic regions on the disk become too small, they cannot retain their magnetic orientations -- the data - over the typical lifetime of the product. This is called the "superparamagnetic effect," and has long been predicted to appear when densities reached 20 to 40 billion bits (gigabits) per square inch, which is near the data density of current products".

The exceedingly skinny ruthenium layer "forces the adjacent layers to orient themselves magnetically in opposite directions. The opposing magnetic orientations make the entire multilayer structure appear much thinner than it actually is. So small, high-density bits can be written easily on AFC media, but they will retain their magnetisation due to the media's overall thickness."

IBM reckons that AFC will enable hard-disk drives to store 100Gb of data per square inch of disk area by 2003. The first products shipping in volume are IBM's Travelstar notebook HDDs, with data densities up to 25.7Gb/inch.

And why the "Pixie Dust" headline? Some IBM researchers are so taken with the properties of Ruthenium, that they are calling it "Pixie Dust". Boffins too can be twee, it seems. ®