Field dependence of non-reciprocal magnons in chiral MnSi

Abstract

Spin waves in chiral magnetic materials are strongly influenced by the Dzyaloshinskii-Moriya interaction resulting in intriguing phenomena like non-reciprocal magnon propagation and magnetochiral dichroism. Here, we study the non-reciprocal magnon spectrum of the archetypical chiral magnet MnSi and its evolution as a function of magnetic field covering the field-polarized and conical helix phase. Using inelastic neutron scattering, the magnon energies and their spectral weights are determined quantitatively after deconvolution with the instrumental resolution. In the field-polarized phase the imaginary part of the dynamical susceptibility ${\chi }^{\prime \prime }(\epsilon ,\mathbf{q})$ is shown to be asymmetric with respect to wavevectors $\mathbf{q}$ longitudinal to the applied magnetic field $\mathbf{H}$, which is a hallmark of chiral magnetism. In the helimagnetic phase, ${\chi }^{\prime \prime }(\epsilon ,\mathbf{q})$ becomes increasingly symmetric with decreasing $\mathbf{H}$ due to the formation of helimagnon bands and the activation of additional spinflip and non-spinflip scattering channels. The neutron spectra are in excellent quantitative agreement with the low-energy theory of cubic chiral magnets with a single fitting parameter being the damping rate of spin waves.

arXiv commentPaper: 10 pages, 5 figures Supplement: 8 pages, 11 figures

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Cited by in corpus (15)

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• Topological magnon band structure of emergent Landau levels in a skyrmion lattice
• Nonreciprocity of spin waves in noncollinear magnets due to the Dzyaloshinskii-Moriya interaction
• Spin excitation spectra in helimagnetic states: proper-screw, cycloid, vortex crystal, and hedgehog lattice
• Skyrmion crystals in centrosymmetric triangular magnets under hexagonal and trigonal single-ion anisotropy
• Kelvin modes of a skyrmion line in chiral magnets and the associated magnon transport
• Essential model parameters for nonreciprocal magnons in multisublattice systems
• Frustration model and spin excitations in the helimagnet FeP
• Non-reciprocal magnons in non-centrosymmetric MnSi
• Polarized inelastic neutron scattering of non-reciprocal spin waves in MnSi
• Confined dipole and exchange spin waves in a bulk chiral magnet with Dzyaloshinskii-Moriya interaction
• Universal spin wave damping in magnetic Weyl semimetals
• Spin-wave directional anisotropies in antiferromagnetic Ba${}_3$NbFe${}_3$Si${}_2$O${}_{14}$
• Spontaneous chirality selection and nonreciprocal spin wave in breathing-kagome antiferromagnets at zero field
• Nonreciprocal magnon excitations by the Dzyaloshinskii-Moriya interaction on the basis of bond magnetic toroidal multipoles