Magnonic band gap and mode hybridization in continuous Permalloy film induced by vertical coupling with an array of Permalloy ellipses

TL;DR

This study explores how a periodic array of permalloy ellipses coupled with a continuous permalloy film creates tunable magnonic band gaps and mode hybridization, with potential for reprogrammable spin wave devices.

Contribution

It demonstrates experimentally and numerically that vertical coupling with nanodots induces magnonic band gaps and mode hybridization in a continuous film, enabling reprogrammable magnonic properties.

Findings

Magnonic band gap opens at the Brillouin zone border.

Band splitting occurs at smaller wavenumbers due to mode interaction.

Shape anisotropy enables control of spin wave dynamics.

Abstract

We investigate magnonic band structure in thin homogeneous permalloy film decorated with periodic array of elliptically shaped permalloy dots and separated by non-magnetic Pt spacer. We demonstrated experimentally formation of the magnonic band structure for Damon-Eshbach wave propagating in permalloy film with the band gap opened at the Brillouin zone border and band splitting at smaller wavenumbers, due to the Bragg interference and interaction of propagating wave of the continuous film with a standing resonant mode of the nano-ellipses, respectively. The shape anisotropy of the permalloy nanodots allows to control the spin wave dynamics through the switch between two states of the magnetization with respect to the underneath film magnetization, thus enabling magnonic band structure reprogrammability. With numerical analysis we show, that predominant role in formation of the magnonic band structure is played by a vertical dynamic coupling between propagating wave in the film and magnetization oscillations in the nanodots.