Magnetic fields created by skyrmions in a two-dimensional sheet of material composed of iron, germanium, and tellurium. Credit: Argonne National Laboratory
Small magnetic whirlpools could revolutionize high-performance computer memory storage.
Magnets create invisible fields that attract certain materials. A familiar example is refrigerator magnets. However, they also play a vital role in storing data in computers. By exploiting the direction of the magnetic field (for example, up or down), microscopic bar magnets can each store one bit of memory as a zero or one, which is the basis of computer language.
Scientists at the U.S. Department of Energy’s Argonne National Laboratory are working on replacing these bar magnets with tiny magnetic vortices, known as skyrmions. These vortices, which are as small as billionths of a meter, form in certain magnetic materials and have the potential to bring about a new generation of microelectronics for memory storage in high-performance computers.
“The bar magnets in computer memory are like shoelaces tied with a single knot; it takes almost no energy to undo them,” said Arthur McCray, a Northwestern University graduate student working in Argonne’s Materials Science Division (MSD). And any bar magnets malfunctioning due to some disruption will affect the others.
“By contrast, skyrmions are like shoelaces tied with a double knot. No matter how hard you pull on a strand, the shoelaces remain tied.” The skyrmions are thus extremely stable to any disruption. Another important feature is that scientists can control their behavior by changing the temperature or applying an electric current.
Change of skyrmion groupings from highly ordered to disordered with temperature from -92 F (204 kelvin) to -272 F (104 kelvin). Bright dots indicate order. Credit: Argonne National Laboratory
Scientists have much to learn about skyrmion behavior under different conditions. To study them, the Argonne-led team developed an artificial intelligence (AI) program that works with a high-power electron microscope at the Center for Nanoscale Materials (CNM), a DOE Office of Science user facility at Argonne. The microscope can visualize skyrmions in samples at very low temperatures.
The team’s magnetic material is a mixture of iron, germanium, and tellurium. In structure, this material is like a stack of paper with many sheets. A stack of such sheets contains many skyrmions, and a single sheet can be peeled from the top and analyzed at facilities like CNM.
“The CNM electron microscope coupled with a form of AI called machine learning enabled us to visualize skyrmion sheets and their behavior at different temperatures,” said Yue Li, a postdoctoral appointee in MSD.
“Our most intriguing finding was that the skyrmions are arranged in a highly ordered pattern at minus 60 degrees Fahrenheit and above,” said Charudatta Phatak, a materials scientist and group leader in MSD. “But as we cool the sample the skyrmion arrangement changes.” Like bubbles in beer foam, some skyrmions became larger, some smaller, some merge, and some vanish.
At minus 270, the layer reached …….