Tunable Snell's law for spin waves in heterochiral magnetic films

TL;DR

This paper derives a tunable Snell's law for spin waves in heterochiral magnetic films, enabling control over spin-wave refraction and guiding through magnetic field adjustments, with potential applications in magnonic devices.

Contribution

It introduces an analytical model for spin-wave refraction at DMI interfaces, including a tunable Snell's law and critical angles, advancing magnonic control in heterochiral magnetic structures.

Findings

Derived an analytical expression for spin wave propagation angles.

Formulated a generalized, tunable Snell's law for spin wave refraction.

Identified asymmetric Brewster angles controllable by magnetic field.

Abstract

Thin ferromagnetic films with an interfacially induced DMI exhibit nontrivial asymmetric dispersion relations that lead to unique and useful magnonic properties. Here we derive an analytical expression for the magnon propagation angle within the micromagnetic framework and show how the dispersion relation can be approximated with a comprehensible geometrical interpretation in the k-space of the propagation of spin waves. We further explore the refraction of spin waves at DMI interfaces in heterochiral magnetic films, after deriving a generalized Snell's law tunable by an in-plane magnetic field, that yields analytical expressions for critical incident angles. The found asymmetric Brewster angles at interfaces of regions with different DMI strengths, adjustable by magnetic field, support the conclusion that heterochiral ferromagnetic structures are an ideal platform for versatile spin-wave guides.