Bloch point mediated vortex switching

Summary form only given. The switching of the core of a vortex in a thin film by a perpendicular field has been predicted, on topological grounds, to occur through the creation and displacement of a Bloch point (BP). With the recently obtained MFM pictures of vortex cores, experimental observation of this process becomes possible. The authors present numerical 3-D micromagnetics simulations, using the public code OOMMF. The material parameters were permalloy-like, damping parameter /spl alpha/=0.5, thickness=50 nm. The samples were disks, diameter 100-400 nm; the mesh size was always below the exchange length /spl Lambda/=5 nm.