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  • Open Access

Bulk-Mediated Reflection of Chirality-Protected Surface Spin Waves

Vitaliy I. Vasyuchka1,*, Florin Ciubotaru2,*, Andrii V. Chumak3, Burkard Hillebrands1, and Alexander A. Serga1,†

  • *These authors contributed equally to this work.
  • †Contact author: serha@rptu.de
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Phys. Rev. Lett. 137, 176701 – Published 21 October, 2026

DOI: https://doi.org/10.1103/hgvh-s6h5

Abstract

Surface spin waves of the Damon-Eshbach type exhibit intrinsically nonreciprocal transport properties with a chiral dynamical field structure that localizes counterpropagating waves at opposite film surfaces. Such chirality has been predicted to suppress direct backscattering in thin films within frequency ranges free of bulk modes. However, how chirality influences reflection in thicker three-dimensional magnetic media, where a dense spectrum of bulk excitations overlaps with surface waves, remains unclear. Here we demonstrate that, in micrometer-thick yttrium iron garnet films, reflection of the chiral Damon-Eshbach wave from the boundary of the magnetic medium is accompanied by excitation of spatially localized thickness-quantized bulk modes, whereas reciprocal backward-volume waves reflect nearly elastically. Brillouin light scattering spectroscopy, infrared thermography, and micromagnetic simulations reveal standing bulk excitations at the reflecting boundary and quantify the associated magnon energy accumulation and dissipation. These results identify bulk-mode excitations as the physical pathway enabling reversal of chirally localized surface waves in thick films, thereby defining the limits of chirality-based backscattering immunity and providing a general framework for wave transport in nonreciprocal magnetic media.

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References (28)

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Phys. Rev. Lett. 137, 176701– Published 21 October, 2026
  • Received 6 March 2026
  • Revised 22 June 2026
  • Accepted 21 September 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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