Exotic and controllable collective magnetic excitations in a chiral helimagnet ${\mathrm{Cr}\mathrm{Nb}}_3{\mathrm{S}}_6$ make it an ideal candidate for exploring emergent electromagnetic phenomena and developing magnon-based devices. Here, we experimentally investigate the polarization properties of the magnetic excitations in a ${\mathrm{Cr}\mathrm{Nb}}_3{\mathrm{S}}_6$ single crystal using circular polarization resolved spectroscopy. An external magnetic field controlled the magnetic structure from a chiral soliton lattice (CSL), consisting of chiral soliton kinks and ferromagnetic domains, to the forced ferromagnet (FFM) phase, and conventional and circular dichroism microwave spectra are observed over a wide frequency range. The observed magnetic excitations, including a CSL phonon mode, Kittel-like mode, and band structures likely due to the excitation of magnetostatic waves, are well characterized by distinct polarization properties. These results visualize the local spin dynamics in the CSL and the influence of the Dzyaloshinskii–Moriya interaction in the FFM phase, aiding the fundamental understanding of the spin dynamics in chiral helimagnets.

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• Chirality
• Magnetic texture
• Magneto-optical effect
• Spin dynamics
• Spin waves
• Helimagnets
• Solitons
• Microwave techniques