Imagine a computer as powerful as the one sitting on your desktop-but small enough to fit into your shirt pocket. Or try a less ambitious concept: Turn on your PC and watch your software programs come up instantly. Gone is all that tedious booting up. As a bonus, you won’t lose your work when the fuse blows.
Both of these concepts could grow out of the emerging field known as “spintronics.” Experts say instant-on memory could hit the market in five years, and the miniaturization of computing enabled by spintronics will then gain momentum as the technology moves out of the R&D pipeline.
In today’s computers, a divide separates the system’s logic from its long-term memory. The central processing unit (CPU) and the short-term memory called RAM (random-access memory) operate by electronics. The hard disk, where the long-term memory resides, stores memory magnetically. Magnetic storage is great for packing in vast amounts of data and, unlike most existing semiconductor memory, it can store information permanently. But so far, magnetic-based memory has lacked the speed needed to keep up with real-time computing. That’s why you need to reboot every time you start up your personal computer: Your PC is shifting the programs from the hard disk to the semiconductor-based RAM memory.
Now physicists and computer scientists are learning the magnetic tricks that could close this divide. At least 10 corporate labs, including those at IBM, Motorola, Hewlett-Packard and startup Integrated Magnetoelectronics, are working on prototypes of magnetic RAM (MRAM). The new memory chips promise an unmatched combination of instant-on capability, reduced power consumption, speed and density.
The technology needed to make all this come true is magnetoelectronics, or simply spintronics. It exploits magnetic properties in layers of materials only a few atoms thick, taking advantage of an electron’s spin as well as its charge. “We are manipulating these structures on the atomic scale…something people didn’t think was possible even 10 years ago,” says Stuart Parkin, a physicist at IBM’s Almaden Research Center in San Jose, Calif., and a pioneer in the field.
Already, Parkin’s work on one early form of spintronics-giant magnetoresistance,” or GMR-has revolutionized the hard-drive industry by giving read-heads the ability to detect much tinier bits (see “The Big, Bad Bit Stuffers of IBM,” TR July/August 1998). But today’s most feverish research-by Parkin and others in corporate and government labs-is focused on MRAM, using a form of spintronics called “magnetic tunnel junctions.” Devices that incorporate these junctions are similar to conventional RAM with a key exception: They rely on the quantum effect of electrons tunneling from one magnetic layer to another to write and read binary bits of information.
MIT physicist Jagadeesh Moodera–who built the first tunnel-junction device five years ago with his MIT colleague Robert Meservey–predicts MRAM could make hard drives obsolete. “Instead, you will have nonvolatile RAM, and that means you will have no more moving parts,” he says.
Long-term, the linking of a tiny MRAM chip to a tiny magnetic CPU-with no need for a hard disk-could be a boon for miniaturization and pervasive computing. “Eventually a whole computer based on spin-that’s the idea, that’s the vision,” says Stuart Wolf, program manager at the Defense Advanced Research Projects Agency, which has been a strong financial backer of spintronics. Such a computer, says Wolf, would be at least three orders of magnitude faster and use less power than conventional models. In addition, it “will be a hell of a lot smaller-to get the same computing power as you have in the box sitting on your desk, probably 1,000 times smaller.”
That’s going to take at least 20 years. Then what? Computers based on the spin of single electrons, Wolf says. “These spin devices will be the ultimate in nanoscale,” he says. “You can’t get any smaller than an elementary