Abstract
is a metallic ferrimagnet displaying signatures of both topological electrons and topological magnons arising from ferromagnetism and spin-orbit coupling within its Mn kagome layers. Inelastic neutron scattering measurements find strong ferromagnetic (FM) interactions within the Mn kagome layer and reveal a magnetic bandwidth of . The low-energy magnetic excitations are characterized by strong FM Mn-Mn and antiferromagnetic (AFM) Mn-Tb interlayer magnetic couplings. We observe weaker, competing long-range FM and AFM Mn-Mn interlayer interactions similar to those driving helical magnetism in the system. Combined with density-functional theory calculations, we find that competing Mn-Mn interlayer magnetic interactions occur in all compounds with , Gd-Lu, resulting in magnetic instabilities and tunability when Mn- interactions are weak. In the case of , strong AFM Mn-Tb coupling ensures a highly stable three-dimensional ferrimagnetic network.
1 More- Received 1 November 2021
- Revised 24 February 2022
- Accepted 18 March 2022
DOI:https://doi.org/10.1103/PhysRevX.12.021043
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
Topological quantum materials have “tangled” electronic bands in their bulk that are “freed” on their surfaces, revealing a metallic character. These unusual electronic states can result in unique properties for next-generation devices, such as resistanceless quantized surface electrical conduction while the bulk of the material remains insulating. Magnetic topological materials have the advantage that magnetism can leverage the topology to generate even more unique phases. Therefore, understanding their fundamental magnetic interactions is vitally important. Here, we report inelastic neutron scattering results that quantify the fundamental magnetic interactions in the magnetic topological metal .
In this material, magnetic manganese (Mn) layers that host topological electronic states sandwich layers of magnetic terbium (Tb) atoms. We observe strong Mn-Mn intralayer ferromagnetic interactions and antiferromagnetic Tb-Mn interlayer interactions, resulting in a rigid layered ferrimagnetic structure. We also observe weaker long-range Mn-Mn interlayer interactions, which are either ferromagnetic or antiferromagnetic, resulting in magnetic competition.
Combining these results with calculations, we find that competing Mn-Mn interlayer magnetic interactions occur in —where can be yttrium or the rare-earth metals gadolinium through lutetium—offering enhanced tunability of magnetic order and of the topological state. Our results further suggest that the variety of magnetic instabilities found in these compounds at high temperatures or high magnetic fields may be understood by a transferable set of magnetic interactions.
A complete understanding of these interactions and their evolution through the family could allow for the prediction of additional topological responses accessible by tuning the magnetism using external fields or changing the rare-earth ion.