New Spin for Electronics

Computerworld - Imagine a data storage device the size of an atom, working at the speed of light. Imagine a microprocessor whose circuits could be changed on the fly. One minute, it would be optimized for database access, the next for transaction processing and the next for scientific number-crunching.
Finally, imagine a computer memory thousands of times denser and faster than today's memories. And nonvolatile, so it retains its contents when the power is off.
All of these and more are on computing's horizon, thanks to the exploding field of spintronics. Spintronics, from "spin transport electronics," isn't entirely new. The spintronic effect called giant magneto-resistance was introduced by IBM in 1997 in its GMR disk-read head. As a result, disk capacities have jumped by a factor of 100 in the past five years.
Electronic circuits are driven by electron flows, which have a charge that can be measured and controlled. But electrons not only flow; they also spin like tiny bar magnets. Depending on their orientation, the spins are said to be "up" or "down."
This additional variable, or "degree of freedom," means that electrons can do more things and convey more information than they do in conventional electronics. "Spin gives you an additional knob to turn," explains Stuart Wolf, a program manager at the Defense Advanced Research Projects Agency (DARPA), which is funding much of the spintronics research in the U.S.
The most immediate research goal is to produce magnetic random-access memory (MRAM), which stores data using magnetism rather than electrical charges. Unlike the dynamic RAM in your PC, MRAM is nonvolatile.
IBM is working with Munich-based Infineon Technologies AG and says it will have MRAM in production as early as 2005. It will be 50 times faster than DRAM and 10 times denser than static RAM, and it could eventually replace both, says Stuart Parkin, an IBM fellow at the company's Almaden Research Center in San Jose.
Others have even suggested that MRAM might replace disks for data storage. Putting logic and storage in a single chip would eliminate the slow disk I/O that's a bottleneck in most computer processing.
IBM's MRAM will use magnetic tunnel junctions, an application of spintronics in which electrons are allowed to "tunnel" between two ferromagnetic layers based on their spin. Each junction can store one bit. "It promises a sort of universal RAM with very high performance -- high writing and reading speeds -- plus very high density and nonvolatility," Parkin says.
Nuclear Memories
Further out, researchers are working on still more exotic applications of spin. David Awschalom, director of the Center for