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PHYSICISTS may have overcome a major stumbling block on the road to
“spintronics”, a potentially powerful new kind of electronics designed to take
advantage of the fact that electrons have spin, rather like subatomic tops.

Spintronics aims to control streams of electrons that are polarised with
their spin axes pointing in the same direction. Their spin could be used to
encode data, or perhaps ultimately in quantum computers that perform many
simultaneous calculations. But there has always been a technical hurdle:
spin-polarised current doesn’t stay that way when it flows out of a wire and
into a semiconductor—which is what microchips are made of.

Now it turns out that current retains its spin-polarisation much better if
the interface between the metal wire and the semiconductor is hard for the
electrons to penetrate, says a team led by Berend Jonker, a physicist at the
Naval Research Laboratory in Washington DC.

Jonker’s team injected current from a iron wire that had been magnetised,
which spin-polarised the electrons, into an aluminium gallium arsenide
semiconductor. They adjusted the make-up of the semiconductor to produce a
“Schottky barrier”—a region that stops electron flow.

However, a quantum effect called tunnelling allowed some of the blocked
electrons to pop through the barrier. Jonker’s team found that 30 per cent of
these were still spin-polarised, even at room temperature. That’s 10 times as
many as have ever been achieved before. Jonker believes the advance opens the
door to the first experimental spintronic devices.