Observation of Binary Vortex Core States in Magnetic Multilayers

Topological spin textures such as skyrmions or vortices are attracting significant attention because of their fundamentally interesting magnetostatic and dynamic properties. In particular, magnetic vortices have been studied intensively during the past decade. Such a spin vortex consists of a planar, flux-closing magnetization curl that tilts out of the plane in the central core. Although being relatively small, the core is of crucial importance for the overall vortex structure. For a stacked trilayer geometry, two basic vortex core configurations can be expected, namely parallel (PL) and antiparallel (AP) cores. In the present contribution, we address the direct observation of both PL and AP core configurations in trilayer vortex pairs. Transmission x-ray microscopy is used to directly image the congruent cores in a Co(48)/Ru(0.8)/Ni81Fe19(43) (nm) trilayer stack. Moreover, switching between both configurations in the same vortex pair was achieved by applying high frequency in-plane magnetic fields.