Spin waves in full-polarized state of Dzyaloshinskii-Moriya helimagnets: Small-angle neutron scattering study

Spin-wave dynamics in the helimagnet FeGe studied by small-angle neutron scattering

“…Despite of being ω-odd, the cross section of the inelastic scattering being integrated over the energy transfer contains the polarization-dependent part due to the peculiarity of the aforementioned asymmetric dispersion relation. As was demonstrated in 16 , one can distinguish the scattering from the helimagnons in a homochiral crystalline sample using polarized neutrons in SANS experiment.…”

“…This fact is related to the completely anisotropic dispersion relation of magnons, which reads for the magnetic field above the critical value H c2 22 . It can be analytically shown that the inelastic scattering of the neutrons in this case is concentrated mostly around the momentum transfers corresponding to ±k s within two narrow cones limited by the cut-off angle θ C for the energy gain/energy loss, respectively 16 . The cut-off angle is connected to the spin-wave stiffness via the dimensionless parameter θ 0 = (2Am n ) −1 :…”

“…Nevertheless, magnetization measurements indicated that the rotation of the helix axis at T 2↓,↑ can be explained by an interplay of constants of 4th and 6th terms of the cubic anisotropy 9 . While the spin-wave dynamic of MnSi has been intensively studied in the past [10][11][12][13][14][15][16] , it was never the case for FeGe, due to the lack of a sufficient large amount of single crystalline samples, which is necessary for the triple axis spectroscopy (TAS). The recently proposed method 16 to determine the spin-wave stiffness in the helical magnets based on DM interaction in the FP state, using polarized small-angle neutron scattering (SANS), can be extended to be used for the polycrystalline FeGe compounds.…”

“…While the spin-wave dynamic of MnSi has been intensively studied in the past [10][11][12][13][14][15][16] , it was never the case for FeGe, due to the lack of a sufficient large amount of single crystalline samples, which is necessary for the triple axis spectroscopy (TAS). The recently proposed method 16 to determine the spin-wave stiffness in the helical magnets based on DM interaction in the FP state, using polarized small-angle neutron scattering (SANS), can be extended to be used for the polycrystalline FeGe compounds. This method was originally developed and applied to measure the spin-wave stiffness in ferromagnetic compounds [17][18][19][20][21] .…”

Magnon dispersion shift in the induced ferromagnetic phase of noncentrosymmetric MnSi

“…Nonetheless, because of the insufficient Q-and E-resolutions, the magnon band shift was only speculative, being far from conclusive. Quite recently an another trial was made to experimentally study the magnon band shift using polarized small angle neutron scattering technique 28 . In the experiment, polarization dependence of the energy integrated diffraction intensity was recorded, and from its Q-space asymmetry the magnon dispersion shift was inferred.…”