Scientists find way to store bits on magnets but without any electric current
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December 29, 2014
A new team of research scientists at Cornell University have discovered a new method to
store data bits on magnets, but without needing electric current. The secret is in using
bismuth ferrite instead of traditional methods.
The team's new magneto electric memory device has two-step magnetic switchability feature with
nothing but an electric field, the team says.
Furthermore, it doesn't need any voltage to turn it on and detect its polarity. The finding has
resulted in a whitepaper called "Deterministic switching of ferromagnetism at room temperature using
an electric field", which has been published in Nature.
The researchers made their device from bismuth ferrite (BiFeO3). This is a multiferroic material,
being magnetic, with north and south poles like any 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 normally.
Previously, bismuth ferrite was thought to be unusable but the discovery of this new two-step
process has changed things quite a bit.
Now, data can be encoded without current by an electric field applied across an insulator, requiring
very 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)
"Our results suggest new ways to engineer magnetoelectric switching and tailor technologically
pertinent functionality for nanometre-scale, low-energy-consumption, non-volatile magnetoelectronics,"
the scientific team said.
The research group includes Cornell post-doctoral 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.
Specifically, multiferroics became interesting to scientists 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," Heron added.
In June 2003, Ramesh discovered that bismuth ferrite could be grown in extremely thin films
exhibiting some rather interesting properties and this helped pave the way to the BiFeO3 device
as we know it today.
If this interesting technology is to find its way into actual products, then development
engineers will need to figure out how this new method stacks up against STT-RAM and other various
Source: Cornell University.
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