Direct Observation of Binary Vortex Core States in Magnetic Mutlilayers

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. As shown in Fig. 1(a), such a spin vortex consists of a planar, flux-closing magnetization curl that tilts out of the plane in the central core. Vortices are typically found as the ground state of micron sized ferromagnetic thin film elements, whi- le their nanoscopic cores are being much smaller, with diameters on the order of 10 nm only. Along with fundamental investigations, proposals were also made to apply vortices for memory cells, or as oscillators in data communication devices. In this view, stacking of vortices via nonferromagnetic interlayers [cf. Fig. 1(b)] is an important issue to address, since such geometries allow for the exploitation of GMR/TMR as well as spin-torque effects.