Researchers are using 2D magnetic materials for energy-efficient computing.  MIT News

This example shows an electric current being pumped into the platinum (bottom slab), resulting in an electron spin current that changes the magnetic state of the 2D ferromagnet above. Colored circles represent atoms in a 2D material. Credit: Massachusetts Institute of Technology

Experimental computer memories and processors made from magnetic materials use much less energy than traditional silicon-based devices. Two-dimensional magnetic materials, composed of layers that are only a few atoms thick, have incredible properties that can allow magnetic-based devices to achieve unprecedented speed, efficiency, and scalability.

Although many hurdles must be overcome until these so-called van der Waals magnetic materials can be integrated into working computers, MIT researchers have demonstrated the precise control of van der Waals magnets at room temperature. An important step in this direction was taken by demonstrating.

This is key, because magnets made of atomically thin van der Waals materials can usually only be controlled at very cold temperatures, making them difficult to deploy outside the laboratory.

The researchers used pulses of electric current Magnetization at room temperature. Magnetic switching can be used in computation, the same way a transistor switches between open and closed to represent 0s and 1s in binary code, or in computer memory, where the switching enables data storage. Published in research. Nature Communications.

The team fired bursts of electrons at a magnet made of a new material that can retain its magnetism at high temperatures. The experiment took advantage of a fundamental property of electrons called spin, which makes electrons behave like miniature magnets. By manipulating the spin of the electrons that strike the device, the researchers can change its magnetism.

“The heterostructure device we developed requires a low-level electric current to switch the van der Waals magnet,” says Deblina Sarkar, AT&T Career Development Assistant Professor at the MIT Media Lab and Center. , compared to that required for bulk magnetic devices.” for Neurobiological Engineering, head of the Nanocybernetic Biotrack Lab, and senior author of a paper on the technique. “Our device is also more energy efficient than other van der Waals magnets that are unable to switch at room temperature.”

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

“There’s a lot of inertia around trying to improve materials that have worked well in the past,” says Shivam. In retrospect, you can potentially come up with a much better solution,” says Shivam. Kajale is a graduate student in Sarkar’s lab and co-lead author of the paper.

Atomically thin gain

Methods of making tiny computer chips in a clean room from bulk materials like silicon can block devices. For example, a material layer may be barely 1 nanometer thick, so small rough spots on the surface can be severe enough to degrade performance.

In contrast, van der Waals magnetic materials are internally layered and structured in such a way that the surface remains perfectly smooth, even when researchers peel back the layers to make thinner devices. In addition, atoms in one layer will not leak into other layers, which enables the material to retain its unique properties when stacked into devices.

“In terms of scaling up 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 Typically only operated at temperatures below 60 Kelvin (-351 degrees Fahrenheit). To create a magnetic computer processor or memory, researchers need to use an electric current to drive a 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 required for effective room-temperature magnetism and does not contain the rare earth elements, which are undesirable because their extraction is particularly destructive to the environment.

Nguyen carefully grew bulk crystals of this 2D material using a special technique. Then, Kajale created 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 called spin to change magnetism at room temperature.

Electron Ping Pong

Although the electrons don’t technically “spin” like the top, they have the same angular momentum. This spin has one direction, either up or down. Researchers can take advantage of a property known as spin-orbit coupling to control the spin of electrons fired at the magnet.

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

In a sense, this transition rotates the magnetization from top to bottom (or vice versa), so it is called a “torque” as in spin-orbit torque switching. Applying a negative electric pulse causes the magnetization to move downward, while a positive pulse moves it upward.

The researchers can do this switching at room temperature for two reasons: the special properties of iron gallium telluride and the fact that their technique uses a small amount of electrical current. Putting too much current into the device will cause it to overheat and become magnetized.

Kajale says the team faced many challenges over the two years to achieve this milestone. Finding the right magnetic material was only half the battle. Because iron gallium telluride oxidizes rapidly, it is important to fabricate inside nitrogen-filled gloves.

“The device is only exposed to air for 10 or 15 seconds, but then I still have to do a step where I polish it to remove any oxide,” he says.

Now that they have demonstrated. Switching and higher energy efficiency, researchers plan to further advance the performance of magnetic van der Waals materials.

“Our next milestone is to achieve switching without the need for an external magnetic field. Our goal is to expand our technology and scale up to bring the potential of van der Waals magnets into commercial applications,” says Sarkar. .

More information:
Shiv N. Kajale et al., Current-Induced Switching of Van der Waals Ferromagnets at Room Temperature, Nature Communications (2024). DOI: 10.1038/s41467-024-45586-4

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Reference: Researchers are using 2D magnetic materials to save energy

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