Soft-X-ray momentum microscopy of nonlinear magnon interactions below 100-nm wavelength

Steffen Wittrock; Christopher Klose; Salvatore Perna; Korbinian Baumgaertl; Andrea Mucchietto; Michael Schneider; Josefin Fuchs; Victor Deinhart; Tamer Karaman; Dirk Grundler; Stefan Eisebitt; Bastian Pfau; Daniel Schick

doi:10.1038/s41567-026-03318-z

arXiv · 2504.20958

Soft-X-ray momentum microscopy of nonlinear magnon interactions below 100-nm wavelength

Steffen Wittrock·Christopher Klose·Salvatore Perna·Korbinian Baumgaertl·Andrea Mucchietto·Michael Schneider·Josefin Fuchs·Victor Deinhart·Tamer Karaman·Dirk Grundler·Stefan Eisebitt·Bastian Pfau·Daniel Schick

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Abstract

Magnons are quantised collective excitations of long-range ordered spins. At nanometre wavelengths, exchange interactions increasingly govern their dynamics, giving rise to a largely unexplored regime of couplings between magnons and other quasiparticles. Yet, detecting such short-wavelength spin waves has remained a key experimental challenge. Here, we introduce Magnon Momentum Microscopy (MMM) -- a quasi-elastic, resonant magnetic soft-X-ray scattering technique that directly images magnon populations across two-dimensional momentum space. Owing to its remarkable sensitivity, MMM can capture nonlinear magnon-magnon interactions over large regions of the dispersion plane. Applying MMM to the prototypical magnonic material yttrium iron garnet (YIG), we uncover a rich variety of previously unobserved nonlinear magnon interactions. With its element specificity, bulk sensitivity, as well as intrinsic access to nanometre-scale wavelengths without frequency limitation, soft-X-ray MMM establishes a powerful and versatile platform for exploring short-wavelength and nonlinear magnonics.

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Steffen Wittrock, Christopher Klose, Salvatore Perna, Korbinian Baumgaertl, Andrea Mucchietto, Michael Schneider, Josefin Fuchs, Victor Deinhart, Tamer Karaman, Dirk Grundler, Stefan Eisebitt, Bastian Pfau, Daniel Schick. 2025-04-29. Soft-X-ray momentum microscopy of nonlinear magnon interactions below 100-nm wavelength. https://doi.org/10.1038/s41567-026-03318-z

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