IBM's scanning tunneling microscope captured this image
of a byte of data, shown in eight 12-atom increments. Those other bumps are
stray xenon atoms. (Image: IBM)
IBM researchers have found a way to put a single bit of data on a 12-atom surface, creating the world’s smallest magnetic storage device.
It’s a breakthrough that’s not likely to make its way into hard drives or memory sticks for decades, but it gives us a hint at how much road lies ahead for magnetic storage devices.
Before now, physicists really didn’t know how small they could take magnetic storage before the laws of quantum mechanics would take over, making it impossible to reliably store data. String together 8 atoms, for example, and you simply can’t get a stable magnetic state, says Andreas Heinrich, the IBM researcher behind the discovery. “The system will just spontaneously hop from one of those states to another state in a timescale that is too fast for us to claim anything like a data storage [demonstration]. It might be switching 1,000 times per second.”
Another problem: how to keep neighboring bits of data from interfering with each other? Today’s hard drives store data in what’s known as a ferromagnetic structure. This is how a compass needle or a refrigerator magnet work: They have lots of atoms lumped together, all pointing in the same magnetic directions.
IBM’s 12-atom bit-keeper uses an antiferromagnetic structure, however, meaning that the atoms point in opposite directions. This keeps the atoms from interfering with each other, an important feature when you’re storing data just 12 atoms at a time. “In a ferromagnet all of these atoms add together to make a big spin and that big spin interacts with the neighboring big spin. And so you cannot control these independently anymore,” Heinrich says. “But in an antiferromagnet there is no big spin, and so you can put these guys very close together”
Heinrich did his work using a scanning tunneling microscope (STM), something that IBM researchers invented 30 years ago, which allows them to see and move around atoms.
12-atom storage devices would be much, much smaller than today’s disks. Heinrich’s friends at hard-drive maker Hitachi estimate that their storage drives require about 800,000 atoms per bit.
So what’s keeping the atom-scale flash drive from showing up at your local Best Buy? Well, first off, they operate at 1 degree kelvin. That’s about -458 Fahrenheit. Bump things up to room temperature and Heinrich thinks it would take about 150 atoms per bit.
And there’s an even bigger problem. Nobody has a clue how to build something this small outside of the lab. And certainly, nobody can do it cheaply, Heinrich says. “That is something that many people are working on, but nobody has solved it yet.”
Still, when Heinrich got his first glimpse at the 12 atoms holding a charge in his STM last spring, he was mesmerized. He sat at his Almaden lab for four hours straight, switching the tiny clump of atoms back and forth between magnetic states. “I was basically just blown away,” he says. “Every once in a while, even we who work with this kind of stuff on an almost daily basis get blown away that it is actually possible.”
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