Propagation of Spin Waves Through an Interface Between Ferromagnetic and Antiferromagnetic Materials

TL;DR

This paper derives boundary conditions for spin wave propagation across a ferromagnetic-antiferromagnetic interface, analyzing how spin waves are transmitted, reflected, and excited at the interface considering exchange interactions and finite interface thickness.

Contribution

It introduces a continuous medium approximation approach to boundary conditions at FM/AFM interfaces, accounting for finite interface thickness and exchange interactions, to analyze spin wave transmission and reflection.

Findings

Derived boundary conditions for FM/AFM interfaces.

Calculated transmission and reflection coefficients for spin waves.

Analyzed excitation of surface evanescent spin waves.

Abstract

Boundary conditions for order parameters at an interface between ferromagnetic (FM) and two-sublattice antiferromagnetic (AFM) materials were obtained in the continuous medium approximation similarly to the approach which allows one to take into account the finite thickness of the FM/FM interface, which is much less than spin wave length. Three order parameters are considered inside an interface of finite thickness with the magnetization $\mathbf{\text{M}}$ of FM, magnetizations of both sublattices $\mathbf{\text{M}}_{1}$ and $\mathbf{\text{M}}_{2}$ of AFM. The uniform and non-uniform exchange between all order parameters are taken into account to the interface energy. Using these boundary conditions, the excitation of a surface evanescent spin wave is considered in AFM when the spin wave in FM falls onto this interface. The coefficients and the phases of transmission and reflection of spin wave through the FM/AFM interface are derived.