Magnetic interactions and excitations in SrMnSb_2
arxiv(2024)
摘要
The magnetic interactions in the antiferromagnetic (AFM) Dirac semimetal
candidate SrMnSb_2 are investigated using ab initio linear response
theory and inelastic neutron scattering (INS). Our calculations reveal that the
first two nearest in-plane couplings (J_1 and J_2) are both AFM in nature,
indicating a significant degree of spin frustration, which aligns with
experimental observations. The orbital resolution of exchange interactions
shows that J_1 and J_2 are dominated by direct and superexchange,
respectively. In a broader context, a rigid-band model suggests that electron
doping fills the minority spin channel and results in a decrease in the AFM
coupling strength for both J_1 and J_2. To better compare with INS
experiments, we calculate the spin wave spectra within a linear spin wave
theory framework, utilizing the computed exchange parameters. The calculated
spin wave spectra exhibit overall good agreement with measurements from INS
experiments, although with a larger magnon bandwidth. Introducing additional
electron correlation within the Mn-3d orbitals can promote electron
localization and reduce the magnetic coupling, further improving the agreement
with experiments.
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