Revolutionary "Racetrack" Memory Computer Technology Breakthrough
Spintronics might sound like a particularly loud techno DJ, but it's an advance in computing technology that could lead to a revolutionary new memory. All the speed of flash memory, all the size of hard disks, and none of the old-age burnout of either.
Electronics is based on the movement of electrons (hence the name). We've known that electrons carry a small, definite amount of charge since the eighteen-nineties - it just took a while to work out how to build things like iPods out of them. The fact that they also have a value called 'spin', a quantum number based on their intrinsic angular momentum, was discovered thirty years later - and we're finally getting around to using that too.
The new memory is based on the combination of the very advanced and the very simple. The very advanced is recent progress in the field of spintronics, using nano-fabricated materials to access and manipulate "spin currents", flows of spin-polarized electrons. The very simple is looking at existing microchips and saying "isn't there an awful lot of room on top of those things?"
Current microchip architecture is very two-dimensional, efforts to expand it into 3-D limited by the horrendous complexity of layering and connecting multiple chips in a stack. The new "Racetrack Memory" takes advantage of this extra space, erecting a vertical nanowire which can contain a spin-based data, 'racing' back and forth along the track past a reader at the bottom. You can think of it as combining the advantages of both current memory systems - each location is immediately accessible and readable, like a flash chip, but each contains a lot of data, like an extremely rapidly moving hard disk.
This racing data is made possible by the physics of spin-momentum transfer, whereby pulses of spin-current can shift all the data in the nanowire back or forward. The structure is know as a "current-controlled magnetic domain-wall nanowire shift register", which is probably why they gave it a snappy name like "racetrack" - they don't want people to die of fright (or old age) when they read out the full title.
Not that super-dense memory is a supreme selling point of spintronics. Flash chips and hard disks continue to advance rapidly, and people who would have laughed at the idea of gigabyte storage five years ago now walk around with more than that in their phones. Further expansions in memory, up to the tera, peta, and exabyte levels aren't going to astonish anyone.
What's important is that it's a definite demonstration of the utility of spintronics. Still a developing field, with unresolved issues remaining to be worked out before we start slinging around spintronic storage, such snazzy demonstrations are vital to keep interest (and funding) alive. Obvious imitations of existing electronics is a great place to start - saying "like what you have, but better and cheaper!" will get anyone's interest - but it isn't the whole point. The science of spintronics enables operations that simple charge-shuffling can't emulate - we just have to get the spinny nuts and bolts worked out before we decide how to use them.
One thing's for sure: with such immediately accessible applications keeping people aware of the field, it won't be long before we start seeing some truly spintronic innovations.
Posted by Luke McKinney.
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