A blueprint for producing exceptionally powerful and efficient data storage in computer chips, among other applications, is the promise of a research breakthrough at Cornell University that allows the control of atomically-thin magnets with an electric field.

The work reaches back to a theory from over half a century ago, when Cornell physicist David Mermin and his postdoc Herbert Wagner theorized that 2D magnets could not exist if the spins of their electrons could point in any direction. It wasn’t until 2017 that some of the first 2D materials with the proper alignment of spins began to be discovered — opening the door to a new family of materials known as 2D van der Waals magnets.

“If it’s a bulk material, you can’t easily access the atoms inside,” explains Kin Fai Mak, an assistant professor of physics and one of the authors of a paper on the new research. “But if the magnet is just a monolayer, you can do a lot to it. You can apply an electric field to it, put extra electrons into it, and that can modulate the material properties.”

The team set out to do just that with a sample of chromium triiodide. Their goal was to apply a small amount of voltage to create an electric field and control the 2D compound’s magnetism, which would allow them to switch the magnet on and off. To achieve this, they stacked two atomic layers of chromium triiodide with atomically-thin gate dielectrics and electrodes. This created a field-effect device that could flip the electron-spin direction in the chromium triiodide layers using small gate voltages, activating the magnetic switching. The process is reversible and repeatable at temperatures under 57 degrees Kelvin.

While the majority of existing electronics technology is based on magnetic switching, for the most part these magnets do not respond to an electric field. In order to switch the magnet on and off, a magnetic field must be created by a current being passed through a coil — an inefficient method because the current creates heat and consumes electrical power. But 2D chromium-triiodide magnets have a unique advantage: An electric field can be directly applied to activate switching, which requires very little energy.

The team plans to continue exploring 2D magnets; one goal they have is to find new 2D magnetic materials that unlike chromium triiodide, can work at room temperature.

The research appears in a recent edition of Nature Materials.