Merging phonons and magnons in periodic ferromagnetic nanostructures

Autor: Scherbakov, Alexey, Godejohann, Felix, Kukhtaruk, Serhii, Poddubny, Alexander, Yaremkevich, Dmytro, Wang, Mu, Nadzeyka, Achim, Yakovlev, Dmitri, Rushforth, Andrew, Akimov, Andrey, Bayer, Manfred
Přispěvatelé: Experimentelle Physik 2, Technische Universität Dortmund [Dortmund] (TU), A.F. Ioffe Physical-Technical Institute, Russian Academy of Sciences [Moscow] (RAS)
Jazyk: angličtina
Rok vydání: 2020
Předmět:
Zdroj: Forum Acusticum
Forum Acusticum, Dec 2020, Lyon, France. pp.3043-3043, ⟨10.48465/fa.2020.0746⟩
Popis: International audience; We demonstrate that in the optically excited periodic ferromagnetic nanostructures the time and spatial evolution of coherent lattice and magnetic excitations, i.e. phonons and magnons, can be drastically modified by the interaction between the localized phonon and magnon modes [1-3]. In our recent experiments we study lateral ferromagnetic nanogratings milled by focus ion beam in a 100-nm layer of metallic alloy (Fe,Ga) epitaxially grown on GaAs substrate [3]. The studied nanogratings of 200-nm period consist of parallel grooves of 100-nm width and 7 ? 21 nm depth milled along [100]- crystallographic direction. The nanograting phonon spectrum contains several localized surface phonon modes of different polarizations with frequency of ~10 GHz and long lifetimes. In a conventional pump-probe experiment we excite the nanograting by a fs- laser pulse and detect the coherent phonon and magnon response by monitoring the intensity and polarization of the probe pulse reflected from the studied structure. By applying an external magnetic field, we tune a certain magnon mode of a broad magnon spectrum into resonance with the localized phonon modes. The manifestation of the resonant magnon-phonon interaction depends on the phonon mode polarization and symmetry as well as its spatial matching with the magnon mode. The most spectacular result is the formation of a coherent magnon polaron, i.e. a mixed state of strongly coupled phonon and magnon modes, which is confirmed by clearly observed avoided crossing. This coupled state is formed by the ground magnon mode and the hidden localized phonon mode, which cannot be accessed by light directly. [1] J. V. J�ger et al., Phys. Rev. B 92, 020404(R) (2015). [2] A. S. Salasyuk et al., Phys. Rev. B 97, 060404(R) (2018). [3] F. Godejohann et al., arxiv.org/abs/1909.01886 (2019).
Databáze: OpenAIRE
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