You can also find vortex rings wherever you have liquids.
Now, scientists have found the art of the vortex interesting somewhere – inside a small column made of magnetic material, the gadolinium-cobalt intermetallic compound GDCO2.
If you’ve seen smoke rings, or bubble rings under water, you’ve seen vortex rings: a donut-shaped venticis that forms when the liquid flows back on itself after being pushed through a hole.
The new discovery is the first time that vortex rings have been identified in magnetic materials, confirming decades-old predictions – and that could help scientists identify even more complex magnetic structures that could be used to develop new techniques.
Magnetic ring vertices were predicted 20 years ago in 1998, when Nigel Cooper, a physicist at Cambridge University, showed that vortex rings are similar to those seen in liquid motility. Indeed, it was very difficult to find them.
In fact, it wasn’t until 2017 when technology developed to bring a chuck into the image of technology into surface-level materials. Researchers at the Paul Sherer Institute and ETH Zurich have developed an X-ray nanotomography technique for the image of a three-dimensional magnet structure in GDCO.2 Bulk magnets.
During those experiments, researchers led by ETH Zurich physicist Claire Donnelly identified vertices that appear when you pull a plug from a sink filled with water. These vertebrates were associated with their topological counterparts, the antiortises.
In the same small GDCO2 Pillars, researchers also found closed magnetic loops, which were also present in the vortex-antivirtex pair. Only after magnetically analyzing these compositions in the context of magnetic vorticity did the team discover that these are sweet-shaped ring vortices, intersected by magnetization singularities – the point at which magnetization disappears – the vortex and the vortex.
(Donnelly et al., Nature Physics, 2020)
Above: A vortex-antivirtex pair. The orange and green box boxes indicate areas where polarization occurs opposite.
But, surprisingly, they do not behave exactly as predicted. Fluid ring vortices are always in motion and do not last very long, so it was expected that the magnetic ring vortices behaved in the same way, turning from the magnetic material before disintegrating.
Instead, the vortices were still sitting in a stable configuration, only to disappear after the GDCO2 Was annealed – exposed to a hot and strong magnetic field, which is used to regenerate the magnet.
Now one of the main puzzles, said Donnelly of Cambridge University, was why these constructions are so unexpectedly static – like smoke rings, they are supposed to exist only as moving objects.
“Through a combination of analytical calculations and consideration of data, we determined the origin of their stability to be magnetostatic interaction.”
In other words, vortices interact with the magnetic structures around them, resulting in stability, which pins the rings in place. Studying how they form and remain stable can help physicists learn how to control magnetic vortex rings, which in turn can help develop better technologies such as data storage and neuromorphic engineering.
But vortex rings can also help to better understand magnetization. For example, the role of uniformity in the magnet process is poorly understood. And observation of vortex rings suggests that more complex structures, such as solitations (magnetic waves), could be studied in more detail.
“Magnetic vorticity and the characterization of three-dimensional structures observed in the calculation and visualization of pre-images have proved to be essential tools,” the researchers wrote in their paper.
“Observation of static magnetic vortex rings opens up possibilities for further study of complex three-dimensional solvents of bulk magnets, enabling the development of applications based on three-dimensional magnetic structures.”
Research has been published in Nature Physics.
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