Magnonic spin-wave modes in CoFeB antidot lattices

TL;DR

This study investigates magnonic spin-wave modes in CoFeB antidot lattices, revealing a novel precessional mode linked to a Bloch state and a field-independent mode, indicating delocalized and localized magnetic excitations.

Contribution

The paper reports the first observation of a Bloch state-related spin-wave mode and a field-independent mode in CoFeB antidot lattices, expanding understanding of magnonic crystal excitations.

Findings

Discovery of a novel precessional mode related to a Bloch state.

Identification of a magnetic mode with frequency independent of external field.

Evidence of both delocalized and localized spin-wave modes in the structures.

Abstract

In this manuscript time-resolved magneto-optical Kerr effect experiments on structured CoFeB films are presented. The geometries considered are two dimensional square lattices of micrometer-sized antidots, fabricated by a focused ion beam. The spin-wave spectra of these magnonic crystals show a novel precessional mode, which can be related to a Bloch state at the zone boundary. Additionally, another magnetic mode of different nature appears, whose frequency displays no dependence on the externally applied magnetic field. These findings are interpreted as delocalized and localized modes, respectively.