Broadband probing magnetization dynamics of the coupled vortex state permalloy layers in nanopillars

TL;DR

This study investigates how the magnetization dynamics of coupled vortex states in layered permalloy nanopillars change under varying magnetic fields and interlayer separations, revealing mode splitting and transitions confirmed by simulations.

Contribution

It provides new insights into the broadband magnetization response of coupled vortex states in layered nanopillars, highlighting the effects of interlayer coupling and vortex chirality on spin wave modes.

Findings

Eigenfrequency splitting induced by in-plane magnetic field.

Transition between in-phase and out-of-phase spin wave modes.

Qualitative agreement with micromagnetic simulations.

Abstract

Broadband magnetization response of coupled vortex state magnetic dots in layered nanopillars was explored as a function of in-plane magnetic field and interlayer separation. For dipolarly coupled circular Py(25 nm)/Cu(20 nm)/Py(25 nm) nanopillars of 600 nm diameter, a small in-plane field splits the eigenfrequencies of azimuthal spin wave modes inducing an abrupt transition between in-phase and out-of-phase kinds of the low-lying coupled spin wave modes. The critical field for this splitting is determined by antiparallel chiralities of the vortices in the layers. Qualitatively similar (although more gradual) changes occur also in the exchange coupled Py(25 nm)/Cu(1 nm)/Py(25 nm) tri-layer nanopillars. These findings are in qualitative agreement with micromagnetic dynamic simulations.