From Ohio State University, Magnetic ‘Hedgehogs’ Could Store Big Data in Small Space

By Laura Arenschield, Ohio State News, Ohio State University

Atomic-scale magnetic patterns resembling a hedgehog’s spikes could result in hard disks with massively larger capacities than today’s devices, a new study suggests. The finding could help data centers keep up with the exponentially increasing demand for video and cloud data storage.

In a study published in the journal Science, researchers at The Ohio State University used a magnetic microscope to visualize the patterns, formed in thin films of an unusual magnetic material, manganese germanide. Unlike familiar magnets such as iron, the magnetism in this material follows helices, similar to the structure of DNA. This leads to a new zoo of magnetic patterns with names such as hedgehogs, anti-hedgehogs, skyrmions and merons that can be much smaller than today’s magnetic bits.

“These new magnetic patterns could be used for next-generation data storage,” said Jay Gupta, senior author of the study and professor of physics, Ohio State. “The density of storage in hard disks is approaching its limits, related to how small you can make the magnetic bits that allow for that storage. And that’s motivated us to look for new materials, where we might be able to make the magnetic bits much smaller.”

To visualize the magnetic patterns, Gupta and his team used a scanning tunneling microscope in his lab, modified with special tips. This microscope provides pictures of the magnetic patterns with atomic resolution. Their images revealed that in certain parts of the sample, the magnetism at the surface was twisted into a pattern resembling the spikes of a hedgehog. However, in this case the ‘body’ of the hedgehog is only 10 nanometers wide, which is much smaller than today’s magnetic bits (about 50 nanometers), and nearly impossible to visualize. By comparison, a single human hair is about 80,000 nanometers thick.

The research team also found that the hedgehog patterns could be shifted on the surface with electric currents, or inverted with magnetic fields. This foreshadows the reading and writing of magnetic data, potentially using much less energy than currently possible.

“There is enormous potential for these magnetic patterns to allow data storage to be more energy efficient,” Gupta said, though he cautions that there is more research to do before the material could be put into use on a data storage site. “We have a huge amount of fundamental science still to do about understanding these magnetic patterns and improving how we control them. But this is a very exciting step.”

This research was funded by the Defense Advanced Research Projects Agency, a research division of the U.S. Department of Defense. Other Ohio State researchers who co-authored this study include Jacob Repicky, Po-Kuwan Wu, Tao Liu, Joseph Corbett, Tiancong Zhu, Shuyu Cheng, Adam Ahmed, Mohit Randeria and Roland Kawakami.

Article: Atomic-scale visualization of topological spin textures in the chiral magnet MnGe

Science has published an article written by Jacob Repicky, Po-Kuan Wu, Department of Physics, The Ohio State University, Columbus, OH 43210, USA, Tao Liu, Department of Physics, The Ohio State University, Columbus, OH 43210, USA, and University of Electronic Science and Technology of China, Chengdu 610054, China, Joseph P. Corbett, Tiancong Zhu, Shuyu Cheng, Adam S. Ahmed, Department of Physics, The Ohio State University, Columbus, OH 43210, USA, N. Takeuchi, J. Guerrero-Sanchez, Centro de Nanociencias y Nanotecnologia, Universidad Nacional Autónoma de México, Apartado Postal 14, Ensenada Baja California, Código Postal 22800, Mexico, Mohit Randeria, Roland K. Kawakami, and Jay A. Gupta, Department of Physics, The Ohio State University, Columbus, OH 43210, USA.

Abstract: “Topological spin textures in chiral magnets such as manganese germanide (MnGe) are of fundamental interest and may enable magnetic storage and computing technologies. Our spin-polarized scanning tunneling microscopy images of MnGe thin films reveal a variety of textures that are correlated to the atomic-scale structure. Our images indicate helical stripe domains, in contrast to bulk, and associated helimagnetic domain walls. In combination with micromagnetic modeling, we can deduce the three-dimensional (3D) orientation of the helical wave vectors, and we find that three helical domains can meet in two distinct ways to produce either a “target-like” or a ‘π-like’ topological spin texture. The target-like texture can be reversibly manipulated through either current/voltage pulsing or applied magnetic field, which represents a promising step toward future applications.“