Spindynamics in the antiferromagnetic phases of the Dirac metals $A$MnBi$_2$ ($A=$ Sr, Ca)
Marein C. Rahn, Andrew J. Princep, Andrea Piovano, Jiri Kulda, Yanfeng, Guo, Youguo Shi, Andrew T. Boothroyd
TL;DR
This study measures and models the spin-wave spectra in antiferromagnetic Dirac metal compounds $A$MnBi$_2$ ($A=$ Sr, Ca), finding magnetic dynamics unaffected by Dirac fermions and providing detailed exchange parameters.
Contribution
It provides the first detailed experimental and theoretical analysis of spin dynamics in $A$MnBi$_2$, revealing magnetic interactions independent of Dirac fermion effects.
Findings
Spin gaps of approximately 8-10 meV observed.
Magnon dispersion accurately modeled by linear spin-wave theory.
No detectable influence of Dirac fermions on magnetic dynamics.
Abstract
The square Bi layers in MnBi ( Sr, Ca) host Dirac fermions which coexist with antiferromagnetic order on the Mn sublattice below K (Sr) and 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.
Click any figure to enlarge with its caption.
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
Figure 10
Figure 11
Figure 12
Figure 13
Figure 14Peer Reviews
No public reviews on file for this paper yet. If you reviewed it on a platform where reviews are public (OpenReview, ICLR, NeurIPS, ICML), you can paste yours below so the community can read it here.
Videos
No videos yet. Explain this paper in a talk, walkthrough, or lecture? Add one.