Coupling of ferromagnetic and antiferromagnetic spin dynamics in Mn$_{2}$Au/NiFe thin-film bilayers

TL;DR

This study explores the coupled spin dynamics in Mn₂Au/NiFe bilayers, revealing hybrid resonant modes with frequencies up to 40 GHz, driven by interfacial coupling between ferromagnetic and antiferromagnetic layers.

Contribution

It demonstrates the coupling of ferromagnetic and antiferromagnetic resonance modes in Mn₂Au/NiFe bilayers and models the dependence of hybrid modes on interfacial interactions.

Findings

Two resonant modes observed with frequencies up to 40 GHz

Coupling strength of approximately 1.6 T·nm at room temperature

Hybrid modes depend on AFMR frequencies and interfacial coupling

Abstract

We investigate magnetization dynamics of Mn$_{2}$Au/Py (Ni$_{80}$Fe$_{20}$) thin film bilayers using broadband ferromagnetic resonance (FMR) and Brillouin light scattering spectroscopy. Our bilayers exhibit two resonant modes with zero-field frequencies up to almost 40 GHz, far above the single-layer Py FMR. Our model calculations attribute these modes to the coupling of the Py FMR and the two antiferromagnetic resonance (AFMR) modes of Mn2Au. The coupling-strength is in the order of 1.6 T$\cdot$nm at room temperature for nm-thick Py. Our model reveals the dependence of the hybrid modes on the AFMR frequencies and interfacial coupling as well as the evanescent character of the spin waves that extend across the Mn$_{2}$Au/Py interface