Resonant dynamics of skyrmion lattices in thin film multilayers: Localised modes and spin wave emission

Abstract

The spectral signatures of magnetic skyrmions under microwave field excitation are of fundamental interest and can be an asset for high frequency applications. 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 study Pt/FeCoB/AlO${}_x$ multilayers hosting dense and robust skyrmion lattices at room temperature with Gilbert damping of $\sim 0.02$. We use 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 allow us to identify distinct resonant modes detected in the skyrmion lattice phase. Low ($<$ 2 GHz) and intermediate frequency ($2-8$ GHz) modes involve excitations localised to skyrmion edges in conjunction with precession of the uniform background magnetisation, while a 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 the 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.

Main text and supplemetary information, 31 pages in total, 18 figures

References in corpus (7)

• Advances in the Physics of Magnetic Skyrmions and Perspective for Technology
• Additive interfacial chiral interaction in multilayers for stabilization of small individual skyrmion at room temperature
• Magnon-skyrmion scattering in chiral magnets
• Breathing modes of confined skyrmions in ultrathin magnetic dots
• Chiral Magnonic Edge States in Ferromagnetic Skyrmion Crystals Controlled by Magnetic Fields
• Microwave resonances of magnetic skyrmions in thin film multilayers
• Robust formation of nanoscale magnetic skyrmions in easy-plane thin film multilayers with low damping

Cited by in corpus (1)

• Breathing Modes of Skyrmion Strings in a Synthetic Antiferromagnet