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May 17, 2023

Coherent Correlation Imaging Helps Understand Changes in Magnetic Materials

Brookhaven National Laboratory, Upton, NY On the near-atomic level, magnetism

Brookhaven National Laboratory, Upton, NY

On the near-atomic level, magnetism is made of many ever-shifting kingdoms — called magnetic domains — that create the magnetic properties of the material. While scientists know these domains exist, they are still looking for the reasons behind this behavior.

Now, a collaboration lead by scientists from the U.S. Department of Energy's Brookhaven National Laboratory, Helmholtz-Zentrum Berlin (HZB), the Massachusetts Institute of Technology (MIT), and the Max Born Institute (MBI) published a study in Nature in which they used a novel analysis technique — called coherent correlation imaging (CCI) — to image the evolution of magnetic domains in time and space without any previous knowledge. The scientists could not see the "dance of the domains" during the measurement but only afterward, when they used the recorded data to "rewind the tape."

The "movie" of the domains shows how the boundaries of these domains shift back and forth in some areas but stay constant in others. The researchers attribute this behavior to a property of the material called "pinning." While pinning is a known property of magnetic materials, the team could directly image for the first time how a network of pinning sites affects the motion of interconnected domain walls.

"Many details about the changes in magnetic materials are only accessible through direct imaging, which we couldn't do until now. It's basically a dream come true for studying magnetic motion in materials," said Wen Hu, Scientist at the National Synchrotron Light Source II (NSLS-II) and co-corresponding author of the study.

The researchers expect CCI to help unlock other properties of the microcosm of magnetism — such as degrees of freedom or hidden symmetries — that previously weren't accessible through other techniques. CCI's usefulness also represents a breakthrough beyond magnetic materials since the technique can be transferred to different measurement techniques and research areas. One area that might benefit the most from understanding the movement of magnetic domains on the nanoscale is novel computing. Novel memory technology could leverage special magnetic domains called "skyrmions."

"Skyrmions are interesting for artificial intelligence computing because they possess a property that is similar to our short-term memory," said Felix Büttner, Group Leader at Helmholtz-Zentrum Berlin, Professor at the University of Augsburg and co-corresponding of the study. "In current computing architectures everything is linear, which means that the memory is separated from the processor. This is not an issue for most applications but, for example, it makes speech recognition difficult. In speech recognition, the computing part only processes the incoming words, but doesn't remember what has been said previously. In addition, sending that information back from the memory takes a lot of energy. By using skyrmions, we may be able to harness their short-term memory in some way and avoid these issues," he added.

However, before engineers can develop technology that uses this feature, they first need to understand how to manipulate skyrmions and other magnetic domains. They hope that many other research groups will benefit from CCI. While they prepare for applying CCI to a broader range of previously inaccessible dynamics as well as expanding the technique to other x-ray sources, they’re also working on implementing machine learning to make the CCI analysis less manual and more accessible by an even broader community.

For more information, contact Cara Laasch at This email address is being protected from spambots. You need JavaScript enabled to view it.; 631-344-8000.

This article first appeared in the June, 2023 issue of Tech Briefs Magazine.

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