Vortex dynamics in coupled ferromagnetic multilayer structures

Magnetization dynamics in ferromagnetic multilayer structures was studied by time-resolved transmission x-ray microscopy. A square-shaped 1x1 mu m(2) trilayer structure consisting of Co(20 nm)/Cu(10 nm)/Permalloy Ni80Fe20(20 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 degrees 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. (C) 2006 American Institute of Physics.