Spin wave beam propagation in ferromagnetic thin film with graded refractive index: mirage effect and prospective applications

TL;DR

This paper investigates spin-wave beam propagation in ferromagnetic thin films with graded refractive index, revealing mirage effects and lensing applications, and demonstrating a magnonic waveguide with preserved beam width.

Contribution

It introduces a novel analysis of spin-wave propagation in graded index ferromagnetic films, including mirage effects and a magnonic waveguide concept.

Findings

Demonstrated mirage effect for spin waves with narrowing beam width

Proposed a graded-index lens for spin-wave focusing

Showed long-distance beam preservation in a magnonic waveguide

Abstract

Using analysis of iso-frequency contours of the spin-wave dispersion relation, supported by micromagnetic simulations, we study the propagation of spin-wave (SW) beams in thin ferromagnetic films through the areas of the inhomogeneous refractive index. We compare the transmission and reflection of SWs in areas with gradual and step variation of the SW refractive index. In particular, we show the mirage effect for SWs with narrowing SW beam width, and an application of the gradual modulation of the SWs refractive index as a diverging lens. Furthermore, we study the propagation of SWs in ferromagnetic stripe with modulated refractive index. We demonstrate that the system can be considered as the graded-index waveguide, which preserves the width of the SW beam for a long distance-the property essential for prospective applications of magnonics.