MAY 23--IBM Corp. (Yorktown Heights, NY; www.research.ibm.com) has demonstrated an innovative type of magnetic coating that is expected to increase the data density of hard-disk drives by more than four times to 100 Gbits/sq in. of disk area. The data storage breakthrough involves a three-atom-thick layer of the element ruthenium, a precious metal similar to platinum that is positioned between two magnetic layers.
Called "antiferromagnetically coupled (AFC)" media, the multilayer coating is anticipated to allow hard-disk drives to store 100 Gbits of data per square inch of disk area by 2003. Today, IBM is shipping AFC media in its Travelstar notebook hard-disk drive with data densities to 25.7 Gbits/sq in.
The AFC media solves the superparamagnetic-effect problem, which causes data-storage materials to change their magnetic orientation under very-high-density conditions. The ultrathin ruthenium layer forces adjacent layers to re-orient themselves magnetically in opposite directions. The opposing magnetic orientations make the entire multilayer structure appear thinner than it actually is. As a result, smaller high-density bits can be written on AFC media, and they retain their magnetization due to the media�s overall thickness.
Using AFC media, the 100-Gbit data-density technology is projected to deliver the following capacities within two years:
Desktop drives--400 Gbytes, or the information in 400,000 books
Notebook drives--200 Gbytes, equivalent to the storage capacity of 42 DVDs or more than 300 CDs
IBM's one-inch microdrive---6 Gbytes, or 13 hours of MPEG-4 compressed digital video (about eight complete movies) for hand-held devices.
