Spin waves in the antiferromagnetic topological insulators MnBi<sub>2</sub>Te<sub>4</sub> and MnBi<sub>4</sub>Te<sub>7</sub>

ORAL

Abstract

MnBi2+2nTe4+3n are promising topological insulators (TI) where the natural intergrowth of magnetic layers and TI layers provides a unique platform for the study of interplay between magnetism and topological electronic states. Here we present our inelastic neutron scattering (INS) study on single crystals MnBi2Te4 and MnBi4Te7. We find that antiferromagnetic (AF) interlayer magnetic interactions in MnBi2Te4 which are vanishingly small in MnBi4Te7, need to be anisotropic for a consistent description of both INS and magnetization measurements. The modeling of two-dimensional intralayer ferromagnetic (FM) spin waves requires introduction of long-range and competing FM and AF magnetic interactions up to the seventh nearest neighbor. First principles calculations of insulating MnBi2Te4 support this model. The abnormal spin wave peak widths observed with INS could result from Mn vacancies/ Mn-Bi anti-site exchange as suggested by our spin dynamics simulation.

*This work is supported by the U.S. Department of Energy, Office of BES, DMSE. Ames Laboratory is operated for the U.S. DOE by Iowa State University under Contract No. DE-AC02-07CH11358. This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory.

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Presenters

  • Bing Li

    • Ames Laboratory, Iowa State University, Dept. of Physics and Astronomy, Ames
    • Ames Laboratory and Iowa State Univeristy
    • Ames Laboratory and Iowa State University, Ames, IA USA 50011

Authors

  • Bing Li

    • Ames Laboratory, Iowa State University, Dept. of Physics and Astronomy, Ames
    • Ames Laboratory and Iowa State Univeristy
    • Ames Laboratory and Iowa State University, Ames, IA USA 50011

  • Liqin Ke

    • Ames Laboratory
    • Ames Laboratory, U.S. Department of Energy, Ames, Iowa 50011, USA
    • Iowa State University
    • Ames Laboratory, U.S. Department of Energy

  • Simon Riberolles

    • Physics and Astronomy, Iowa State University/Ames Laboratory
    • Division of Materials Science & Engineering, Ames Laboratory
    • Ames Laboratory and Iowa State Univeristy

  • Daniel Pajerowski

    • Oak Ridge National Lab
    • Oak Ridge National Laboratory

  • Andreas Kreyssig

    • Physics and Astronomy, Iowa State University/Ames Laboratory
    • Department of Physics and Astronomy, Ames Laboratory, Iowa State University
    • Ames Lab/Iowa State
    • Ames Laboratory, Iowa State University, Dept. of Physics and Astronomy, Ames
    • Ames Laboratory and Iowa State Univeristy

  • Benjamin G. Ueland

    • Ames Laboratory, Iowa State University, Dept. of Physics and Astronomy, Ames
    • Ames Laboratory

  • Jiaqiang Yan

    • Materials Science and Technology Division, Oak Ridge National Lab
    • Oak Ridge National Laboratory
    • University of Tennessee
    • Oak Ridge National Lab
    • Materials Science and Technology Division, Oak Ridge National Laboratory
    • Materials Science and Technology, Oak Ridge National Laboratory
    • Oak Ridge National Laboratory, Materials Science and Technology Division

  • Robert J. McQueeney

    • Ames Laboratory, Iowa State University, Dept. of Physics and Astronomy, Ames
    • Ames Laboratory and Iowa State Univeristy