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Circuits that exploit electron spin as well as charge have come a step
closer. Researchers at the University of Groningen in the Netherlands have
forced flowing electrons to spin in a particular direction. To “spin-polarise”
the current, the scientists applied a voltage across a junction between a magnet
and a copper strip. Most of the electrons in a magnet are spin-polarised, and
about 1 per cent remained so when they entered the copper, say the scientists
(Nature, vol 410, p 345). It’s hoped that using spin as well as charge
will one day let computers carry additional information.