Researchers harness 2D magnetic materials for energy-efficient computing

Experimental computer memories and processors built from magnetic materials consume much less power than traditional silicon-based devices. Two-dimensional magnetic materials, composed of layers just a few atoms thick, possess incredible properties that could enable magnetic devices to achieve unprecedented speed, efficiency and scalability.

While many obstacles must be overcome before these Van der Waals magnetic materials can be integrated into working computers, MIT researchers have taken an important step in that direction by demonstrating the precise control of a Van der Waals magnet at room temperature.

This is critical because magnets made of atomically thin Van der Waals materials can typically only be controlled at extremely cold temperatures, making them difficult to deploy outside of a laboratory.

The researchers used pulses of electrical current to change the magnetization direction of the device at room temperature. Magnetic switching can be used in computing, in the same way that a transistor switches between open and closed to represent 0s and 1s in binary code, or in computer memory, where switching allows storage of data. The research is published in Natural communications.

The team fired bursts of electrons at a magnet made from a new material that could maintain its magnetism at higher temperatures. The experiment exploited a fundamental property of electrons known as spin, which makes electrons behave like tiny magnets. By manipulating the spin of the electrons that strike the device, researchers can change its magnetization.

“The heterostructure device we developed requires an order of magnitude lower electric current to switch the Van der Waals magnet, compared to that required for bulk magnetic devices,” explains Deblina Sarkar, assistant professor of career development at AT&T at the MIT Media Lab and Center. for neurobiological engineering, head of the Nano-Cybernetic Biotrek laboratory and lead author of an article on this technique. “Our device is also more energy efficient than other Van der Waals magnets that cannot switch at room temperature.”

In the future, such a magnet could be used to build computers that are faster and use less electricity. It could also enable non-volatile magnetic computer memories, meaning they don’t leak information when powered off, or processors that make complex AI algorithms more energy efficient.

“There’s a lot of inertia when trying to improve materials that have worked well in the past. But we’ve shown that if you make radical changes, starting with rethinking the materials you use, you can potentially get much better solutions,” says Shivam. Kajale, a graduate student in Sarkar’s lab and co-senior author of the paper.

An atomically thin advantage

Methods for making tiny computer chips in a clean room from bulk materials like silicon can hamper the devices. For example, layers of material can be as little as 1 nanometer thick, so tiny bumps on the surface can be severe enough to degrade performance.

In contrast, Van der Waals magnetic materials are inherently layered and structured in such a way that the surface remains perfectly smooth, even when researchers peel back the layers to make thinner devices. Additionally, atoms from one layer will not leak into other layers, allowing materials to retain their unique properties when stacked in devices.

“In terms of scaling and making these magnetic devices competitive for commercial applications, van der Waals materials are the way to go,” says Kajale.

But there is a catch. This new class of magnetic materials generally only works at temperatures below 60 Kelvin (-351 degrees Fahrenheit). To build a computer processor or magnetic memory, researchers must use electric current to operate the magnet at room temperature.

To achieve this, the team focused on an emerging material called iron gallium telluride. This atomically thin material has all the properties necessary for effective magnetism at room temperature and does not contain rare earth elements, which are undesirable because their extraction is particularly destructive to the environment.

Nguyen carefully grew massive crystals of this 2D material using a special technique. Next, Kajale fabricated a two-layer magnetic device using nanoscale flakes of iron gallium telluride under a six-nanometer layer of platinum.

A small device in hand, they used an intrinsic property of electrons known as spin to switch its magnetization at room temperature.

Electronic ping pong

Although electrons don’t technically “spin” like a top, they have the same type of angular momentum. This rotation has a direction, up or down. Researchers can exploit a property known as spin-orbit coupling to control the spins of the electrons they pull onto the magnet.

In the same way that momentum is transferred when one ball hits another, electrons transfer their “spinning momentum” to the 2D magnetic material when they hit it. Depending on the direction of their spins, this momentum transfer can reverse magnetization.

In a sense, this transfer rotates the magnetization up and down (or vice versa), which is why it is called a “torque”, as in spin-orbit torque switching. Applying a negative electrical impulse causes the magnetization to go down, while a positive impulse causes it to go up.

Researchers can perform this switching at room temperature for two reasons: the special properties of iron gallium telluride and the fact that their technique uses small amounts of electrical current. Pumping too much current into the device will cause overheating and demagnetization.

The team faced many challenges over the two years it took to reach this milestone, Kajale says. Finding the right magnetic material was only half the battle. Since iron gallium telluride oxidizes quickly, manufacturing must be carried out in a glove box filled with nitrogen.

“The device is only exposed to air for 10 or 15 seconds, but even after that I have to do a polishing step to remove any oxide,” he explains.

Now that they have demonstrated room temperature switching and greater energy efficiency, the researchers plan to continue improving the performance of Van der Waals magnetic materials.

“Our next step is to achieve switching without the need for external magnetic fields. Our goal is to improve our technology and expand it to bring the versatility of the van der Waals magnet to commercial applications,” said Sarkar .

This story is republished courtesy of MIT News (web.mit.edu/newsoffice/), a popular site that covers news in MIT research, innovation and education.