• Open Access

Low-Temperature Competing Magnetic Energy Scales in the Topological Ferrimagnet TbMn6Sn6

S. X. M. Riberolles, Tyler J. Slade, D. L. Abernathy, G. E. Granroth, Bing Li, Y. Lee, P. C. Canfield, B. G. Ueland, Liqin Ke, and R. J. McQueeney
Phys. Rev. X 12, 021043 – Published 23 May 2022
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Abstract

TbMn6Sn6 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 230meV. 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 YMn6Sn6 system. Combined with density-functional theory calculations, we find that competing Mn-Mn interlayer magnetic interactions occur in all RMn6Sn6 compounds with R=Y, Gd-Lu, resulting in magnetic instabilities and tunability when Mn-R interactions are weak. In the case of TbMn6Sn6, strong AFM Mn-Tb coupling ensures a highly stable three-dimensional ferrimagnetic network.

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  • 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)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

S. X. M. Riberolles1,*, Tyler J. Slade1,2, D. L. Abernathy3, G. E. Granroth3, Bing Li1,2, Y. Lee1, P. C. Canfield1,2, B. G. Ueland1, Liqin Ke1, and R. J. McQueeney1,2,†

  • 1Ames Laboratory, Ames, Iowa 50011, USA
  • 2Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
  • 3Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

  • *simon.riberolles@gmail.com
  • mcqueeney@ameslab.gov

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 TbMn6Sn6.

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 RMn6Sn6—where R 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 RMn6Sn6 family could allow for the prediction of additional topological responses accessible by tuning the magnetism using external fields or changing the rare-earth ion.

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Vol. 12, Iss. 2 — April - June 2022

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