Spin waves represent the collective excitations of themagnetizationfield within a magnetic material, providing dispersion curves thatcan be manipulated by material design and external stimuli. Bulk andsurface spin waves can be excited in a thin film with positive ornegative group velocities and, by incorporating a symmetry-breakingmechanism, magnetochiral features arise. Here we study the band diagramof a chiral magnonic crystal consisting of a ferromagnetic film incorporatinga periodic Dzyaloshinskii-Moriya coupling via interfacial contactwith an array of heavy-metal nanowires. We provide experimental evidencefor a strong asymmetry of the spin wave amplitude induced by the modulatedinterfacial Dzyaloshinskii-Moriya interaction, which generatesa nonreciprocal propagation. Moreover, we observe the formation offlat spin-wave bands at low frequencies in the band diagram. Calculationsreveal that depending on the perpendicular anisotropy, the spin-wavelocalization associated with the flat modes occurs in the zones withor without Dzyaloshinskii-Moriya interaction.

Experimental Observation of Flat Bands in One-Dimensional Chiral Magnonic Crystals

Petti, Daniela;Cattoni, Andrea;Girardi, Davide;Albisetti, Edoardo;
2023-01-01

Abstract

Spin waves represent the collective excitations of themagnetizationfield within a magnetic material, providing dispersion curves thatcan be manipulated by material design and external stimuli. Bulk andsurface spin waves can be excited in a thin film with positive ornegative group velocities and, by incorporating a symmetry-breakingmechanism, magnetochiral features arise. Here we study the band diagramof a chiral magnonic crystal consisting of a ferromagnetic film incorporatinga periodic Dzyaloshinskii-Moriya coupling via interfacial contactwith an array of heavy-metal nanowires. We provide experimental evidencefor a strong asymmetry of the spin wave amplitude induced by the modulatedinterfacial Dzyaloshinskii-Moriya interaction, which generatesa nonreciprocal propagation. Moreover, we observe the formation offlat spin-wave bands at low frequencies in the band diagram. Calculationsreveal that depending on the perpendicular anisotropy, the spin-wavelocalization associated with the flat modes occurs in the zones withor without Dzyaloshinskii-Moriya interaction.
2023
Brillouin light scattering
Dzyaloshinskii−Moriya
chiral magnonic crystals
flat bands
spin waves
thin films
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11311/1251437
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