IBM has managed to store data on a permalloy nanowire using a technique that could yield high data densities, according to the company.

"Until now, manipulating domain walls was complex, and used significant power to generate the fields necessary," said IBM. "This obstacle can be overcome."

Given a magnetic wire of suitable dimensions, IBM has demonstrated that magnetic domain pairs on that wire can be shifted up and down the wire with current pulses and that physical features on the magnetic wire 'pin' the domains in fixed locations when there is no current.

"It takes advantage of the interaction of spin polarised current with magnetisation in the domain walls," said IBM. "This results in a spin transfer torque on the domain wall, causing it to move."

It has also demonstrated that current flowing in a standard conductor passing the magnetic conductor at right angles can write domains of predictable polarity into the permalloy.

The pole pattern across the wall adjoining the domain pair stores a 0 or 1.

"The cycle time for the writing and shifting of the domain walls is a few tens of nanoseconds," said IBM.

To read the data, researches formed a magnetic tunnelling junction further along the permalloy conductor which controls current flow in a third 'readout' wire.

A memory would need many magnetic wires, dubbed 'racetracks', and to save space, IBM is proposing to form them in tall vertical loops (see diagram) with only short horizontal sections over the read and write conductors.