Field- and frequency-tunable magnon-phonon resonances in arrays of ferromagnetic nanostripes studied via time-resolved optical magnetometry

The coupling of lattice and magnetization dynamics is a topic of growing interest, with significant implications for novel solid-state technologies. In this work, we investigate arrays of ferromagnetic Fe/Permalloy nanostripes. A time-resolved optical approach enables the study of magnonic and phononic excitations, as well as their coupling at mode crossings. The field-dependent frequencies were also measured using Brillouin light scattering spectroscopy and corroborated by micromagnetic simulations for different in-plane directions of an external magnetic field. We find that the acoustic and magnonic excitations can be tuned in frequency and magnetic field by adjusting the array periodicity, filling ratio, as well as the orientation of the nanostripes relative to the external field. Additionally, we discuss the presence of features in the signal intensity at the magnon–phonon crossings, introduced by dynamical phase effects due to the impulsive coherent excitation.