Spin-wave spectra in antidot lattice with inhomogeneous perpendicular magnetocrystalline anisotropy

TL;DR

This study uses micromagnetic simulations to analyze how inhomogeneous perpendicular magnetic anisotropy affects spin-wave spectra in a 2D antidot lattice, revealing mode splitting and hybridization phenomena.

Contribution

It demonstrates the impact of edge-modified anisotropy on spin-wave modes and uncovers the mechanisms of mode hybridization in magnonic crystals.

Findings

Spectral splitting into bulk and edge modes due to anisotropy variation

Strong hybridization between bulk and rim modes at resonance

Exchange interactions influence higher-order mode coupling

Abstract

Magnonic crystals are structures with periodically varied magnetic properties that are used to control collective spin-wave excitations. With micromagnetic simulations, we study spin-wave spectra in a 2D antidot lattice based on a multilayered thin film with perpendicular magnetic anisotropy (PMA). We show that the modification of the PMA near the antidot edges introduces interesting modifications to the spin-wave spectra, even in a fully saturated state. In particular, the spectra split in two types of excitations, bulk modes with amplitude concentrated in a homogeneous part of antidot lattice, and edge modes with an amplitude localized in the rims of reduced PMA at the antidot edges. Their dependence on the geometrical or material parameters is distinct but at resonance conditions fulfilled, we found strong hybridization between bulk and radial edge modes. Interestingly, the hybridization between the fundamental modes in bulk and rim is of magnetostatic origin but the exchange interactions determine the coupling between higher-order radial rim modes and the fundamental bulk mode of the antidot lattice.