We can change a bit from 0 to 1 WITHOUT CURRENT, say boffins

There could be some iron in the non-volatile soul. A team of Cornell university boffins using bismuth ferrite have discovered a way to store bits on magnets without needing electric current-based switching.

Their room-temperature magnetoelectric memory device has 2-step magnetic switchability "with nothing but an electric field". It doesn't need voltage to turn it on and detect its polarity; bit value in digital terms.

The boffinry has resulted in a paper, "Deterministic switching of ferromagnetism at room temperature using an electric field", which has been published in Nature.

We're told the researchers made their device from bismuth ferrite (BiFeO₃). This is a multiferroic material, being magnetic, with north and south poles like any bog-standard magnet, and also ferroelectric, meaning it's electrically polarized. The polarization can be switched with an electric field. It's a rare property and other multiferroic materials require coldness approaching near-absolute-zero, 4 Kelvin (-452° Fahrenheit) to work.

Previously bismuth ferrite was thought to be unusable but the discovery of the 2-step process involved has changed things. Now data could be encoded without current, for example "by an electric field applied across an insulator," requiring low energy.

The energy involved when using the device is said to be an order of magnitude lower than that needed for spin-transfer torque memory (STT-RAM).

The Nature paper mentions "unambiguous magnetoelectric coupling" and says that "weak ferromagnetism arises from the canting of the antiferromagnetically aligned spins by the Dzyaloshinskii–Moriya (DM) interaction".

Err ... we became mentally numbed at that point, returning to life with the last sentence of the abstract: "our results suggest ways to engineer magnetoelectric switching and tailor technologically pertinent functionality for nanometre-scale, low-energy-consumption, non-volatile magnetoelectronics."

Aha, very dense non-volatile memory is in prospect.

The team of boffins includes Cornell postdoctoral associate John Heron and Darrel Schlom, professor of industrial chemistry in the Materials Science and Engineering Deparment, Ramamoorthy Ramesh, Heron's PhD adviser, and Dan Ralph, physics professor in the College of Arts and Sciences.

Multiferroics became interesting to boffinry around the turn of the century, Schlom said: "Ever since multiferroics came back to life around 2000, achieving electrical control of magnetism at room temperature has been the goal."

Ramesh found in 2003 that bismuth ferrite could be grown in extremely thin films exhibiting interesting properties and this helped pave the way to the BiFeO₃ device.

If this interesting technology is to find its way into actual products then development engineers in memory fabs will need to suss it out and see how it stacks up against STT-RAM and other DRAM follow-on contenders. ®