A new spin on battery technology

Researchers at the Universties of Miami, Tokyo and Tohoku have discovered a new form of battery. Charged by the application of a very strong magnetic field, the Magnetic Tunnel Junction (MTJ) contains a set of nano-magnets - zones some 5 nanometers across in a zinc-gallium-arsenic-mangnesium matrix - which absorb energy and then release it over time. Although the effect had been predicted, the size and duration of the result was not "We had anticipated the effect, but the device produced a voltage over a hundred times too big and for tens of minutes, rather than for milliseconds as we had expected," said one of the researchers. "That this was counterintuitive is what lead to our theoretical understanding of what was really going on."

The MJT is the top part of the illustration, and is roughly the same diameter as a human hair. Beneath that is a magnified image of the central part of the device: the white spots are atoms, and the circles contain the nano-magnets that store the power. Picture: Phan Nam Hai/University of Miami

I've yet to dig out the paper in Nature to find out how far this is from being useful as a power source - as the current device is a few hundred micrometers across, it's not going to be storing megawatts. But it's the sort of thing that could be created in vast arrays, like any semiconductor device, and if they're getting to the bottom of the underlying physics then the same effect could be used in many different configurations. What may be much more interesting than just power storage is the fact, mentioned almost in passing in the press release, that the current delivered by the MTJ is spin-polarised; the electrons are predominately spinning in one direction.

That's hot news for spintronics, which we've covered previously and which, together with graphene, has the most exciting potential for fundamentally new computational devices. Spin logic could work much faster at much lower power than even today's finest electronics, because it doesn't rely on currents flowing and the consequent unavoidable loss.

And, as the researchers say, if this discovery leads to new insights into basic magnetic theory, there are almost no limits to how profoundly it could affect modern life. Which is a bit over the top - just not that much.