Nonlinear spin-wave scattering – three-magnon processes

Speaker: Prof. Maciej Krawczyk

Affiliation: Institute of Spintronics and Quantum Information (ISQI), Faculty of Physics and Astronomy, Adam Mickiewicz University, Poznań, Poland

The development of information technology needs to be characterised by faster, miniaturised and more energy-efficient information processing to meet the growing expectations of modern society. Since the frequency range of spin waves is from a few GHz to a few hundred GHz, the corresponding wavelengths can be very short, from micrometres to a few nm, and their transmission does not involve charges, magnonics can play a role in the realisation of green-edge computing elements based on Boolean and neuromorphic logic [1]. One of the necessary ingredients of these devices is a non-linearity that allows the realisation of the transistor in the first case and the spiking function in artificial neural networks in the second. Since the magnetization dynamics in a ferromagnet is described by the torque equation preserving the length of the magnetization, i.e. the Landau-Lifshitz-Gilbert equation, the spin-wave dynamics in any ferromagnet is inherently non-linear, offering a number of processes for its exploitation. I will concentrate on processes involving three magnons in the particle picture description, i.e. the splitting and confluence processes that have been the focus of our recent investigations. In particular, I will present a inelastic scattering of the spin-wave beam on the localised spin-wave mode [2-4], which in some cases can be used to demonstrate stimulated scattering, an analogue of stimulated Brillouin scattering known from optics. I will also present a promising (to me at least) approach to excite high frequency (above 20 GHz) and very short wavelength (below 100 nm) spin waves using magnonic crystals [5]. This method exploits a three-magnon nonlinear process occurring in the magnonic crystal under a low-frequency microwave magnetic field pump to generate the high-frequency harmonic spin-wave modes of very short wavelengths. Finally, I will discuss the potential of three-magnon processes for information processing applications.

This work was supported in part by the National Science Center Poland project OPUS-LAP no 2020/39/I/ST3/02413 and European Union’s Horizon Europe research and innovation program under Grant Agreement No. 101070347-MANNGA.

[1] A. V. Chumak, et al., Advances in magnetics roadmap on spin-wave computing, IEEE Trans. Magn. 58, 0800172 (2022).

[2] N. N. Dadoenkova, Y. S. Dadoenkova, I. L. Lyubchanskii, M. Krawczyk, and K. Y. Guslienko, Inelastic spin-wave scattering by Bloch domain wall flexure oscillations, Phys. Status. Solidi RRL 2019, 1800589 (2019).

[3] P. Gruszecki, I. L. Lyubchanskii, K. Y. Guslienko, and M. Krawczyk, Local nonlinear excitation of sub-100 nm bulk-type spin waves by edge-localized spin waves in magnetic films, Appl. Phys. Lett. 118, 062408 (2021).

[4] P. Gruszecki, K. Y. Guslienko, I. L. Lyubchanskii, and M. Krawczyk, Inelastic spin-wave beam scattering by edge-localized spin waves in a ferromagnetic thin film, Phys. Rev. Appl. 17, 044038 (2022).

[5] N. Kumar, P. Gruszecki, M. Gołębiewski, J. W. Kłos, and M. Krawczyk, Exciting high-frequency short-wavelength spin waves using high harmonics of a magnonic cavity mode, Adv. Quantum Technol. 2024, 2400015 (2024).