Design of magnonic waveguides using surface anisotropy-induced Bragg mirrors

TL;DR

This paper presents a novel magnonic waveguide design utilizing surface anisotropy-induced Bragg mirrors in a ferromagnetic layer, enabling high-frequency spin wave propagation with improved confinement and reduced demagnetizing effects.

Contribution

It introduces a new waveguide design that employs surface anisotropy to create Bragg mirrors, enhancing spin wave guidance and confinement in magnonic systems.

Findings

High-frequency spin waves can be guided with high velocities.

Surface anisotropy effectively confines spin waves in the waveguide.

The model accurately predicts dispersion and localization of modes.

Abstract

Waveguides are fundamental components for signal transmission in integrated wave-based processing systems. In this paper, we address the challenges in designing magnonic waveguides, including limitations such as non-uniform demagnetizing fields, reduced group velocity, and restricted operating frequency ranges. We propose a magnonic waveguide design with promising properties that overcome these limitations to a significant extent. Specifically, we investigate a waveguide formed within a uniform ferromagnetic layer (Co$_{20}$Fe$_{60}$B$_{20}$) by applying surface anisotropy in strip regions, thereby creating Bragg mirror structures to confine spin waves and guide them along a single direction. The proposed waveguide enables the propagation of high-frequency spin waves with high velocities in the ferromagnetic layer while minimizing static demagnetizing effects. We developed a model that allows for spin-wave confinement and guidance in two perpendicular directions by spatially modulating the surface anisotropy. The theoretical model was solved using the finite element method to calculate the dispersion relations of the waveguide modes and analyze their spatial profiles. Additionally, we determine the group velocity and localization characteristics, providing a comprehensive understanding of the waveguide's performance.