Researchers at the U.S. Department of Energy’s Ames National Laboratory have discovered a method to control magnons, tiny magnetic waves with potential for future quantum technologies. While studying Kagome metals, the team observed strikingly different behavior between materials like TbMn6Sn6, where magnons cross without interacting, and ErMn6Sn6, where they avoid crossing.
“We looked at it and said, ‘Well, that’s funny. I wonder why that is.’ And then we started to realize, wait that’s a left-handed magnon. And that’s a right-handed magnon. Okay, now they’re mixing,” said scientist Rob McQueeney, describing the serendipitous observation that allows switching magnon handedness with minimal energy.
Ferrimagnets Enable Control of Left- and Right-Handed Magnons
The ability to manipulate magnon handedness with minimal energy input represents an advance in controlling these magnetic waves, according to research from Ames National Laboratory. Magnons in the former material crossed paths without interaction, while those in ErMn6Sn6 demonstrably interacted and avoided crossing, a surprising contrast within the same material class.
This disparity highlighted the potential for external control over magnon behavior, a previously unresolved challenge in the field. Ferrimagnets are uniquely suited to this research because their internal structure naturally supports both right- and left-handed magnons, stemming from the presence of two distinct magnetic atoms with unequal magnetic moments.
The team discovered that, under specific conditions, these normally separate magnon states can mix, effectively allowing a switch in a magnon’s handedness with a relatively low energy expenditure. “Magnons have certain advantages for moving information,” explained Rob McQueeney, “But manipulating the handedness was not a solved problem.” The initial observation of this phenomenon occurred serendipitously while studying Kagome metals, materials known for their unusual magnetic properties.
“And that’s a right-handed magnon. Okay, now they’re mixing.” This unexpected mixing of magnon handedness is detailed in the paper “Chiral Magnon Mixing by Symmetry-Breaking in Collinear Ferrimagnets,” authored by Dhurba R. Jaishi, Tyler J. Slade, S. X. M. Riberolles and others. Because magnons transmit information without the movement of electrical charge, they offer a pathway to more efficient computing technologies than those currently available.
The ability to readily control and combine right- and left-handed magnons, therefore, provides new opportunities for magnetic-based quantum information technologies. It’s about creating a system where information can be encoded and manipulated with greater precision and lower energy consumption, potentially clearing the way for more powerful and sustainable computing solutions.
We looked at it and said, ‘Well, that’s funny. I wonder why that is.’ And then we started to realize, wait that’s a left-handed magnon. And that’s a right-handed magnon. Okay, now they’re mixing.
Rob McQueeney, Ames Lab Scientist
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