Geometrical complexity of the antidots unit cell effect on the spin wave excitations spectra

TL;DR

This study explores how increasing the geometrical complexity of antidot lattices in permalloy films affects spin wave spectra, combining simulations and experiments to reveal significant spectral modifications relevant for magnonic applications.

Contribution

It introduces new insights into how unit cell complexity and structural modifications influence spin wave behavior in antidot lattices, supported by both theoretical and experimental analysis.

Findings

Small antidots significantly alter spin wave spectra.

Air-gaps cause directional spin wave propagation discrimination.

Spectral changes occur despite similar spin wave amplitude distributions.

Abstract

We have investigated theoretically (with micromagnetic simulations and plane wave method) and experimentally (with ferromagnetic resonance and Brillouin light scattering) three types of antidot lattices (ADLs) based on permalloy thin films with increased complexity of the unit cell: simple square, bi-component square and wave-like ADL. We have found that placing a small additional antidot in the center of the unit cell of the square ADL modify significantly the spin wave spectrum and its dependence on the orientation of the in-plane magnetic field. We also check the further changes of spin wave spectrum resulting from the introduction of air-gaps connecting small and large antidots. In particular, the presence of small antidots change the dependence of the frequency of the fundamental mode on the angle of the in-plane applied magnetic field. The air-gaps strongly discriminates the propagation of spin waves in two principal direction of ADL lattice, orthogonal to each other. In spite of these spectral changes, the spatial distribution of the spin wave amplitude generally preserves some similarities for all three structures. We also highlighted out the role of defects in the ADL in the observed spectra. The obtained results can be interesting for the magnonics applications of the magnonic crystals.