Shrinkable Storage
Capstone in magnetic hard-disk design

Context: In a hard drive, each bit of information is written on magnetic grains inside a hard disk. Engineers have so far squeezed more data into smaller media by using fewer and fewer grains to hold each bit. But hard-disk manufacturers are now up against physical limits on how much their grains can shrink before they become unstable and lose data. Recent work by researchers from the University of Konstanz in Germany and Hitachi reveals a new magnetic medium that could be the basis for the hard drive of the future.

Methods and Results: Manfred Albrecht and colleagues created their hard-disk medium by first putting down a layer of closely packed nanoscale latex spheres. By sprinkling atoms of cobalt and palladium onto the spheres, they created “magnetic caps” that can store a binary digit as the polarity of a magnetic field. But while its polarity can be flipped, the field always remains perpendicular to the thickest part of the caps. So when the cobalt and palladium rain down onto the spheres from directly above, the magnetic field is perpendicular to the disk surface, as in today’s most advanced hard drives. By orienting the layer of spheres at a 45-degree angle to the stream of cobalt and palladium, the authors created a medium that should be more responsive to magnetic fields from a recording head. This could allow manufacturers to use materials that are magnetically more stable than those in conventional hard drives, enabling more-shrinkable magnetic bits.

Why it Matters: Increases in storage density have enabled hard drives to capture markets in portable electronics such as MP3 players and, more recently, cell phones. Advances like those by Albrecht and colleagues could improve hard-drive capacities another tenfold or more, which would greatly reduce the physical size of current systems and enable, for instance, a new generation of portable video devices.

Source: Albrecht, M., et al. 2005. Magnetic multilayers on nanospheres. Nature Materials 4:203-206.