Resonant subwavelength control of the phase of spin waves reflected from a ferromagnetic film edge

TL;DR

This paper demonstrates how the phase of spin waves reflected from a ferromagnetic film edge can be precisely controlled using a bilayer structure, enabling advanced magnonic device functionalities.

Contribution

It introduces a method to control spin wave phase via bilayer dimensions, revealing a magnonic Gires-Tournois interferometer as a metasurface analogue.

Findings

Spin wave phase is highly sensitive to bilayer width and separation.

Fabry-Perot resonances govern the phase control mechanism.

The system functions as a magnonic metasurface for phase manipulation.

Abstract

Using frequency-domain finite element calculations cross-checked with micromagnetic simulations, we demonstrate that the phase of spin waves reflected from an interface between a permalloy film and a bilayer can be controlled by changing dimensions of the bilayer. Treating the bilayer formed by the permalloy film and a ferromagnetic stripe as a segment of a multi-mode waveguide, we show that spin-wave Fabry-Perot resonances of one of its modes are responsible for the high sensitivity of the phase of reflected waves to stripe width and the stripe-film separation. Thus, the system is a unique realization of a fully magnonic Gires-Tournois interferometer based on a two-modes resonator, which can be treated as a magnonic counterpart of a metasurface, since it enables manipulation of the phase of spin waves at subwavelength distances. Knowledge gained from these calculations might be used to design magnonic devices such as flat lenses or magnetic particle detectors.