spintronics
/ spin-TRON-iks /
An electron has two things going for it: an electric charge, and a tiny built-in magnetism called spin, like a tag that reads either 'up' or 'down.' Ordinary electronics uses only the charge — pushing electrons around to make currents. Spintronics is the bold idea of also using the spin tag, treating it as another handle for carrying and storing information.
The trick is that current flowing through a magnet comes out with its electrons' spins lined up, and a magnet downstream lets such a spin-aligned current pass easily or blocks it, depending on which way that magnet points. Stack two thin magnetic layers and you build a switch whose electrical resistance flips dramatically when one layer's magnetization rotates — a effect called giant magnetoresistance. Reading that resistance reads the direction of a stored magnetic bit, fast and with a feeble signal.
Spintronics matters because it is already inside the device you are using: the read-heads that pulled data off hard disks for decades, and the magnetic memory now creeping into chips, both rest on it. Its promise is memory that keeps its contents with the power off and burns less energy than charge-only electronics. The honest caveat is that controlling spin cleanly is delicate — spins lose their alignment quickly through scattering — so much of the field is the patient hunt for materials and structures where spin survives long enough to be useful.
The 2007 Nobel Prize in Physics honored giant magnetoresistance — the spintronic effect that let hard-disk read-heads sense ever-tinier magnetic bits, and so let drive capacities balloon from megabytes to terabytes within a couple of decades.
Giant magnetoresistance, a spintronic effect, enabled the explosive growth of hard-disk storage.
Spintronics does not necessarily mean no charge moves — most working devices still pass an electric current. The point is that the current's spin, not only its amount, carries and reveals information.