Boffins turned off by silicon switch to TILTING MAGNETS

'Anisotropy': look it up, use it, wear it out

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Solid state memory is already a viable technology at a decent scale, but it's hard to make it small enough to replace hard drives.

However, researchers at the University of California Berkeley are taking a different angle: they would like to shrink high density storage to a size that puts it onto ICs.

Their aim is twofold: to reduce the power computers need (since disks are electricity hogs), while delivering better performance (including much faster power-up, since the processor wouldn't have to load its OS images from disk).

The problem is that like the magnetic particles on a hard drive, nanomagnets on ICs still need an external magnetic field to change their state.

However, in this PNAS paper, associate professor of electrical engineering Sayeef Salahuddin and lead author Long You (who works with Salahuddin) found that by giving nanomagnets the right tilt, they can be switched purely by changing the direction of an applied current.

Tilted nanomagnets image from UC Berkeley

Tilting nanomagnets turns them into nonvolatile memory. Image: UC Berkeley

An electrical current, Salahuddin had already discovered, is enough to set the polarity in nanomagnets using tantalum – a metal familiar to the electronics industry. However, to pack the magnets on a chip in sufficient numbers, they had to be vertically aligned, which spoiled the switching effect.

In the latest work, Salahuddin explains: “We found that by tilting the magnet – just 2 degrees was enough – you get all the benefits of a high-density magnetic switch without the need for an external magnetic field”.

That's the anisotropy mentioned in the subhead: leaving the magnets with vertical alignment makes them symmetrical in all directions (isotropic).

In the abstract of the paper, the boffins explain that their work exploits a property called spin orbit torque (SOT).

Because nothing ever comes for free, tantalum is a rare metal and some of it comes from places like the Congo, bringing with it debate about resources sourced from conflict zones. ®


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