Ultra-narrow spin wave metasurface for focusing application

In this paper we show that the phase shift of the spin waves can be controlled in transmission through metasurface represented as an ultra-narrow non-magnetic spacer separating two ferromagnetic films. We design this metasurface to present the focusing of spin waves in an Co thin film. For this purpose we exploit the strength of the interlayer exchange coupling interactions of RKKY type which allows to control the phase of the transmitted and reflected spin waves in the wide range of angles [$-pi/2$;$pi/2$]. We combined this phase-shift dependency with the lens equation to demonstrate numerically the lens for spin waves based on ultra-narrow metasurface.