Spin waves constitute the building blocks of novel wave computing methods
such as spectral analysis [1], and neuromorphic computing [2], which are all
interference-based techniques. Recently, basics concepts of optics applied to
spin waves demonstrated the possibility to shape and steer spin wave
beams, suggesting prominent performance in particular tasks such as image
processing and speech recognition [3]. However, The complexity of spin
dynamics, inherently due to its dependence to numerous parameters, and
the intricacy of magnon-magnon interactions, requires heavy computational
methods, which can limit the scope of study. In this context, we developed an
efficient tool to study the near-field diffraction (NFD) patterns of spin wave in
homogeneous out-of-plane magnetized thin films for arbitrary distribution of
excitation fields [4, 5].
Here, we present the adaptation of our NFD model to in-plane magnetized
thin films, and reveal how caustic spin-wave beams can be directly emitted
from a sharply constricted stripline. We show in particular the importance of
not only meeting the suitable caustic conditions of field and frequency, but
also having of a seemingly punctual source for shaping the caustic beam [6].
Using spatially resolved micro-focused Brillouin light spectroscopy on various
constriction sizes, we satisfyingly verify our predictions (see Fig. 1), and
explore further the steerability as well as the caustic beams properties (see
Fig. 2). These findings have important implications for future development of
magnonic devices such as spin wave splitters, passive spin-wave frequencydivision
demultiplexers, and wave-based computing building blocks for
neuromorphic architecture.
This work was supported by the French ANR projects “MagFunc”, and
ANR-22-EXSP-0004 “SWING”, the U.S. Department of Energy, Office of
Basic Energy Sciences, Division of Materials Sciences and Engineering
under Award DE-SC0020308, and the Transatlantic Research Partnership, a
program of FACE Foundation and the French Embassy.
References:
[1] A. Papp, W. Porod, A.J. Csurgay, G. Csaba, “Nanoscale spectrum
analyzer based on spin-wave interference”, Scientific Reports 7, 9245,
(2017).
[2] A. Papp, W. Porod, G. Csaba, “Nanoscale neural network using non-linear
spin-wave interference”, Nature Communications 12, 6422, (2021).
[3] E. Albisetti, S. Tacchi, R. Silvani, G. Scaramuzzi, et al., “Optically inspired
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nanomagnonics with nonreciprocal spin waves in synthetic antiferromagnets”,
Advanced Materials 32, 1906439, (2020).
[4] L. Temdie, V. Castel, M. Jungfleisch, R. Bernard, H. Majjad, D. Stoeffler, Y.
Henry, M. Bailleul, and V. Vlaminck. “Probing spin wave diffraction patterns of
curved antennas”, Phys. Rev. Appl. 21, 014032 (2024).
[5] V. Vlaminck, L. Temdie, V. Castel, M.B. Jungfleisch, D. Stoeffler, Y. Henry,
M. Bailleul, “Spin wave diffraction nmodel for perpendicularly magnetized
films”, Journal of Applied Physics 133, 053903, (2023).
[6] D. Wagle, D. Stoeffler, L. Temdie, M. T. Kaffash, V. Castel, H. Majjad, R.
Bernard, Y. Henry, M. Bailleul, M. B. Jungfleisch, and V. Vlaminck, "Shaping
non-reciprocal caustic spin-wave beams", arXiv:2404.15011 (2024)