Vortex dynamics in coupled ferromagnetic multilayer structures

Abstract

Magnetization dynamics in ferromagnetic multilayer structures was studied by time- resolved transmission x-ray microscopy. A square- shaped 11 m2 trilayer structure consisting of Co20 nm/Cu10 nm /Permalloy Ni80Fe2020 nm was investigated. Each ferromagnetic layer showed a Landau-like domain configuration with a single vortex. A gyrotropic vortex motion was excited by an in-plane magnetic field alternating at a frequency of 250 MHz. The movement of the magnetic vortex in each individual magnetic layer was imaged by taking advantage of the element specificity of the x-ray magnetic circular dichroism. A 180° phase shift between the gyrotropic vortex motion in the Permalloy and the Co layer was observed. This phase shift can be ascribed to the magnetic coupling between the layers.