Newly discovered magnetic interactions could lead to new ways to manipulate electron flow
Newly discovered magnetic interactions in the Kagome layered topological magnet TbMn6sn6 could hold the key to adjusting how electrons flow through these materials. Scientists from the United States Department of Energy’s Ames National Laboratory and Oak Ridge National Laboratory conducted an in-depth study of TbMn6sn6 to better understand the material and its magnetic properties. These results could influence future technological advances in areas such as quantum computers, magnetic storage media and high-precision sensors.
Kagomes are a type of material whose structure is named after a traditional Japanese basket weaving technique. The weave produces a pattern of hexagons surrounded by triangles and vice versa. The arrangement of the atoms in Kagome metals reproduces the weave. This property causes electrons in the material to behave in unique ways.
Solid materials have electronic properties determined by the characteristics of their electronic band structure. The band structure is highly dependent on the geometry of the atomic lattice, and sometimes bands can have special shapes, such as cones. These special shapes, called topological features, are responsible for the unique way electrons behave in these materials. The Kagome structure in particular leads to complex and potentially tunable features in the electronic tapes.
Using magnetic atoms to construct the lattice of these materials, such as Mn in TbMn6sn6, may further aid in inducing topological features. Rob McQueeney, a scientist at Ames Lab and the project leader, explained that topological materials “have a special property where under the influence of magnetism you can get currents flowing at the edge of the material, which are dissipationless, meaning the electrons scatter. don’t, and they don’t dissipate energy.”
The team wanted the magnetism in TbMn. better understand6sn6 and used calculations and neutron scattering data collected from the Oak Ridge Spallation Neutron Source to perform their analysis. Simon Riberolles, a postdoc research associate at Ames Lab and member of the project team, explained the experimental technique the team used. The technique involves a beam of neutron particles that is used to test how rigid the magnetic order is. “The nature and strength of the various magnetic interactions present in the materials can all be mapped using this technique,” he said.
They discovered that TbMn6sn6 has competing interactions between the layers, or what is called frustrated magnetism. “So the system has to compromise,” McQueeney said, “usually that means if you poke it, you can make it do different things. But what we found in this material is that even though those competing are interactions there, there are are other interactions that are dominant.”
This is the first detailed investigation of the magnetic properties of TbMn6sn6 be published. “In research, it’s always exciting when you find out that you understand something new, or you’re measuring something that hasn’t been seen before, or was partially or differently understood,” Riberolles said.
McQueeney and Riberolles explained that their findings suggest the material could potentially be modified for specific magnetic properties, for example by changing the Tb for another rare-earth element, which would alter the magnetism of the compound. This fundamental research paves the way for further progress in the discovery of Kagome metals.
This research is discussed further in the article published in Physical Assessment X.
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SXM Riberolles et al, Low temperature competitive magnetic energy scales in the topological ferrimagnet TbMn6Sn6, Physical Assessment X (2022). DOI: 10.1103/PhysRevX.12.021043
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