Close to the limit This hurdle is closer than you might think, says Johnson. That's around 10 -18 cubic centimetres, so at most it will contain just 10 or so charge carriers. That's obviously close to the limit, since you can't make a device with less than one electron. But with metal-based devices, you could make them smaller by at least a factor of 10 and still have enough carriers. It gets better.
Magnetic fields tend to become concentrated as components are shrunk.
And since spintronic devices use magnetic fields to create and hang on to the two populations of charge carriers, their performance actually improves the smaller you make them. He has already built a crude spintronic transistor, and has persuaded others to start taking spintronics seriously. In the early 1990s, Johnson worked at the laboratories of Bellcore in New Jersey. And when they come out the other side, they carry this polarisation with them. This discovery opened the way to the construction of spintronic analogues of familiar electronic devices.