# Chiral excitation of spin waves in ferromagnetic films

## TL;DR

This paper theoretically explores how chiral spin wave excitations occur in ferromagnetic films with nanowire arrays, highlighting the roles of dipolar and exchange couplings and their effects on mode interactions.

## Contribution

It reveals the conditions under which chiral coupling occurs in ferromagnetic nanowire and film systems, emphasizing the suppression of exchange coupling by spacers and the absence of Damon-Eshbach modes.

## Key findings

- Interlayer dipolar coupling matches experimental anticrossings.
- Chiral coupling occurs despite the absence of Damon-Eshbach modes.
- Strong exchange coupling suppresses chirality.

## Abstract

We theoretically investigate the interlayer dipolar and exchange couplings for an array of metallic magnetic nanowires grown on top of an extended ultrathin yttrium iron garnet film. The calculated interlayer dipolar coupling agrees with observed anticrossings [Chen \emph{et al.}, Phys. Rev. Lett. \textbf{120}, 217202 (2018)], concluding that the interlayer exchange coupling is suppressed by a spacer layer between the nanowires and film. The Kittel mode in the nanowire array couples chirally to spin waves in the film, even though Damon-Eshbach surface modes do not exist. The chirality is suppressed when the interlayer exchange coupling becomes strong.