Titiksha Srivastava1, 2, Yanis Sassi1, Fernando Ajejas1, Aymeric Vecchiola1, Igor Ngouagnia2, Hervé Hurdequint2, Karim Bouzehouane1, Nicolas Reyren1, Vincent Cros1, Thibaut Devolder3, Joo-Von Kim3, Grégoire de Loubens2
1 Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Saclay, Palaiseau, France
2 SPEC, CEA, CNRS, Univ. Paris-Saclay, Gif-sur-Yvette, France
3 Centre for Nanoscience and Nanotechnology, CNRS, Univ. Paris-Saclay, Palaiseau, France
The spectral signatures of magnetic skyrmions under microwave field excitation are of fundamental interest and can be an asset for high frequency applications [1,2]. These topological solitons can be tailored in multilayered thin films, but the experimental observation of their spin wave dynamics remains elusive, in particular due to large damping. Here, we present a study of [Pt/FeCoB/AlOx] multilayers hosting dense and robust skyrmion lattices at room temperature with Gilbert damping of ∼0.02 [3]. We used magnetic force microscopy to characterise their static magnetic phases and broadband ferromagnetic resonance to probe their high frequency response. Micromagnetic simulations reproduce the experiments with accuracy and allowed us to identify distinct resonant modes detected in the skyrmion lattice phase. The low (< 2 GHz) and intermediate frequency (< 8 GHz) modes feature excitations dominantly localised in skyrmion edges and uniform background, respectively. The high frequency (> 12 GHz) mode corresponds to in-phase skyrmion core precession emitting spin waves into uniform background with wavelengths in the 50–80 nm range commensurate with lattice structure. These findings could be instrumental in the investigation of room temperature wave scattering and the implementation of novel microwave processing schemes in reconfigurable arrays of solitons.
References
[1] B. Satywali, et al., Nat. Commun. 12, 1909 (2021).
[2] L. Flacke et al., Phys Rev B 104, L100417 (2021).
[3] T. Srivastava et al, arXiv:2111.11797 [cond-mat.mes-hall].