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CRASH-PROOF processor chips that crunch magnetic data rather than the electronic stuff could soon be on the way. Like a computer鈥檚 hard disc drive they鈥檒l continue to store data after a power cut, but they鈥檒l also be impervious to radiation, making them ideal for use in spacecraft.

The first step towards such a chip has been taken by Russell Cowburn and a team at the University of Durham, who have made a magnetic 鈥淣OT gate鈥�. This is the simplest digital logic gate, which simply flips digital 1s to 0s and vice versa. Cowburn鈥檚 device exploits 鈥渟pintronic鈥� phenomena鈥攗sing the fact that electrons have spin that can be aligned by a magnetic field.

He started by etching a splayed Y-shaped nanowire from a film of nickel-iron alloy. The material is ferromagnetic, which means it鈥檚 capable of becoming a permanent magnet. In a normal piece of ferromagnetic material, the spins of electrons within tiny regions or 鈥渄omains鈥� all point the same way. When the material is unmagnetised, the domains are oriented at random, but they all line up when exposed to a strong external field.

In a nanowire, however, the domains can only align themselves with the wire, and the boundary where opposite domains meet can be used to represent a digital 1 or 0, depending on whether the opposing fields meet head to head or tail to tail. The Durham team鈥檚 breakthrough has been to show that with a suitably shaped Y, it is actually possible to use an external magnetic field to switch the domain junctions from one state to the other.

Cowburn says magnetic chips using such Y-shaped NOT gates would have big advantages over electronic ones. 鈥淚f the power fails, it just stops where it is,鈥� he says. 鈥淪o when the power comes on again, it just carries on from where it left off.鈥� And because the magnetic circuits are made of metal they can work without special shielding in high-radiation environments like space, unlike traditional microchips.