Spindynamics in the antiferromagnetic phases of the Dirac metals $A$MnBi${}_2$ ($A=$ Sr, Ca)

Abstract

The square Bi layers in $A$MnBi${}_2$ ($A=$ Sr, Ca) host Dirac fermions which coexist with antiferromagnetic order on the Mn sublattice below $T_{\mathrm{N}}=290$K (Sr) and $270$K (Ca). We have measured the spin-wave dispersion in these materials by triple-axis neutron spectroscopy. The spectra show pronounced spin gaps of 10.2(2)meV (Sr) and 8.3(8)meV (Ca) and extend to a maximum energy transfer of 61 - 63meV. The observed spectra can be accurately reproduced by linear spin-wave theory from an Heisenberg effective spin Hamiltonian. Detailed global fits of the full magnon dispersion are used to determine the in-plane and inter-layer exchange parameters as well as on the magnetocrystalline anisotropy constant. To within experimental error we find no evidence that the magnetic dynamics are influenced by the Dirac fermions.

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• Structural and magnetic phase transitions in the ternary iron arsenides SrFe2As2 and EuFe2As2
• Quantum Hall effect in a bulk antiferromagnet EuMnBi${}_2$ with magnetically confined two-dimensional Dirac fermions
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• Itinerant Spin Excitations in SrFe2As2 Measured by Inelastic Neutron Scattering
• Topological and Transport Properties of Dirac Fermions in Antiferromagnetic Metallic Phase of Iron-Based Superconductors
• Interplay of Dirac electrons and magnetism in AMnBi2 (A=Ca, Sr)
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Cited by in corpus (14)

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• Signatures of coupling between spin waves and Dirac fermions in YbMnBi${}_2$
• Quantum oscillations and Dirac dispersion in the BaZnBi2 semimetal guaranteed by local Zn vacancy order
• Absence of Dirac states in BaZnBi${}_2$ induced by spin-orbit coupling
• Robust antiferromagnetic spin waves across the metal-insulator transition in hole-doped BaMn${}_2$As${}_2$
• Quasi-2D magnetism and origin of the Dirac semimetallic behavior in nonstoichiometric Sr${}_{1-y}$Mn${}_{1-z}$Sb${}_2$ (y, z~$<$0.1)
• Spin dynamics of a magnetic Weyl semimetal Sr${}_{1-x}$Mn${}_{1-y}$Sb${}_2$
• Spin Dynamics in the Antiferromagnetic Oxypnictides and Fluoropnictides: LaMnAsO, LaMnSbO, and BaMnAsF
• Magnetic excitations in the topological semimetal ${\mathrm{YbMnSb}}_2$
• Coupling of magnetism and Dirac fermions in YbMnSb2
• Spin waves in Dirac semimetal Ca${}_{0.6}$Sr${}_{0.4}$MnSb${}_2$ investigated with neutrons by the diffraction method