Could antiferromagnetic chips replace silicon?

Attractive properties of antiferromagnetic memory would include greater density of transistors than silicon provides and immunity to magnets erasing data.

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We probably wouldn’t have a Digital Age without silicon.

The second most abundant element in the Earth’s crust (oxygen is No. 1), silicon is cheap and has the ability to conduct electricity and/or act as an insulator. Converted into silicon wafers, it powers the computers, smartphones and other electronic devices we use to work and, importantly, to avoid work. So clearly silicon is indispensable.

Or maybe not. Our insatiable demand for more and more data, along with the need to store it, is pushing the limits of what silicon can deliver in terms of speed, density, and security. In a bid to find a worthy successor to silicon-based memory devices, MIT physicists are zeroing in something called antiferromagnets.

As Jennifer Chu of the MIT News Office writes:

"Antiferromagnetic, or AFM, materials are the lesser-known cousins to ferromagnets, or conventional magnetic materials. Where the electrons in ferromagnets spin in synchrony—a property that allows a compass needle to point north, collectively following the Earth’s magnetic field—electrons in an antiferromagnet prefer the opposite spin to their neighbor, in an “antialignment” that effectively quenches magnetization even at the smallest scales."

(You should be grateful Jennifer Chu is explaining this. I got a D in chemistry one quarter in eighth grade because I stopped paying attention for two weeks and things unraveled rather quickly. Only an extra-credit dramatic reading of the periodic table spared me from an F.)

"The absence of net magnetization in an antiferromagnet makes it impervious to any external magnetic field. If they were made into memory devices, antiferromagnetic bits could protect any encoded data from being magnetically erased. They could also be made into smaller transistors and packed in greater numbers per chip than traditional silicon."

There’s the money quote: Smaller transistors and packed in greater numbers per chip than traditional silicon. For enterprises that require more data storage capacity in their devices—that is, virtually all enterprises—those are magic words.

“An AFM memory could enable scaling up the data storage capacity of current devices—same volume, but more data,” says Riccardo Comin, assistant professor of physics at MIT and the study’s lead author.

AFM memory, however, likely would have its own challenges and potential limitations. “Every time you need a current to read or write, that requires a lot of energy per operation,” lead author and graduate student Jiarui Li tells Chu. “When things get very small, the energy and heat generated by running currents are significant.”

The MIT team has had some success experimenting with ways to deploy AFM switching more efficiently. (Switching in this context is the process by which data is written onto transistors that can be turned on and off to create a pattern of bits that define a stored image or other digital file. Think the classic 1-and-0 binary code.) In particular, they were able to use a technique called doping—the introduction of impurities into a material—to alter the electronic properties of an AFM oxide called neodymium nickelate and successfully switch AFM on and off.

While the next smartphone or computer you order for your enterprise clearly isn’t going to feature AFM-based storage, the demands of a data-fueled digital economy eventually will require us to move beyond silicon.

“This could present an opportunity to develop a magnetic-memory storage device that works similarly to silicon-based chips, with the added benefit that you can store information in AFM domains that are very robust and can be packed at high densities,” Comin says. “That’s key to addressing the challenges of a data-driven world.”

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