Plasmonic surface lattice resonances, visible in periodic arrays of nanodisks, arise from radiative coupling between the localized surface plasmon resonance1-3 of individual particles and diffracted orders4. Here, we study the impact of these optical modes on the magneto-optical properties5,6 and energy absorption efficiency7 of Co/Gd/PtN nanodisks by measuring the response of different arrays to optical excitations as function of the light wavelength, the disk diameter, and the array period. We demonstrate that surface lattice resonances allow AllOptical single pulse switching8,9 of the nanodisks using much less energy than for the thin film, with an energy absorption enhanced by more than 400 %. Besides, these optical modes increase the magneto-optical Faraday effect by more than 2000 %. The influence of the disk diameter and array period on the amplitude, width and position of the resonances is in qualitative agreement with theoretical calculations and opens the way to design magnetic metasurfaces for all-optical magnetic recording.
References
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2 Savoini, M., et al. Highly efficient all-optical switching of magnetization in GdFeCo microstructures by interference-enhanced absorption of light. Physical Review B, 86:140404, 2012.
3 Cheng, F., et al. All-Optical Manipulation of Magnetization in Ferromagnetic Thin Films Enhanced by Plasmonic Resonances. Nanoletters. 20:6437 – 6443, 2020.
4 Kataja, M., et al. Surface lattice resonances and magneto-optical response in magnetic nanoparticle arrays. Nature Communications, 6:1 – 8, 2015.
5 Freire-Fernández, F., et al. Surface-plasmon-polariton driven narrow-linewidth magneto-optics in Ni nanodisk arrays. Nanophotonics, 9:113 – 121, 2019.
6 Freire-Fernández, F., et al. Magnetoplasmonic properties of perpendicularly magnetized Co/PtN nanodots. Physical Review B, 101:054416, 2020.
7 Kataja, M., et al. Plasmon-induced demagnetization and magnetic switching in nickel nanoparticle arrays. Applied Physics Letters, 112:072406, 2018.
8 Radu, I., et al. Transient ferromagnetic-like state mediating ultrafast reversal of antiferromagnetically coupled spins. Nature, 472:205 – 208, 2011.
9 Lalieu, M. L. M., et al. Deterministic all-optical switching of synthetic ferrimagnets using single femtoseccond laser pulses. Physical Review B, 96:220411, 2017.

Fig. 1. Magnetic Co/Gd/Pt_N metasurface.

Fig. 2. a) Ratio of the All-Optical switching threshold fluence measured on the film and metasurfaces with P = 500 nm and different array diameters. b) Average Faraday readout-sensitivity among 6 samples, defined as the ratio of the Faraday angle of Co/Gd/Pt_N metasurfaces on resonance and in the continuous Co/Gd/Pt_N films at the same wavelength, scaled with the packing density.