Band structure of magnonic crystals with defects: Brillouin spectroscopy and micromagnetic simulations

TL;DR

This study uses Brillouin spectroscopy and simulations to explore the band structures of defected magnonic crystals, revealing tunable defect modes and localized states within the bandgap.

Contribution

First experimental observation of defect-induced band structures in nanostructured magnonic crystals with tunable defect modes.

Findings

Observation of a dispersionless defect branch within the bandgap

Tunable defect mode frequency by varying defect stripe width

Localization of defect mode near the defects

Abstract

Using Brillouin spectroscopy, the first observation has been made of the band structures of nanostructured defect magnonic crystals. The samples are otherwise one-dimensional periodic arrays of equal-width Ni80Fe20 and cobalt nanostripes, where the defects are stripes of a different width. A dispersionless defect branch emerges within the bandgap with a frequency tunable by varying the defect stripe width, while the other branches observed are similar to those of a defect-free crystal. Micromagnetic and finite-element simulations performed unveil additional tiny bandgaps and the frequency-dependent localization of the defect mode in the vicinity of the defects.