Controlling the vortex core of thin Permalloy nano-cylinders dipolar coupled to Co polarizers

We report a theoretical study of the vortex profile of in-plane magnetized PyTM nano-cylinders subjected to the stray field of perpendicular anisotropy Co nano-cylinders. We consider 6 nm thick PyTM cylinders dipolar coupled to 60 nm thick Co cylinders, at distances from 1.5 nm to 30 nm, with diameters (D) ranging from 45 nm to 105 nm. We find considerable reduction of critical diameter for stable PyTM magnetic vortices and spiral-vortex phases, as well as vortex core diameters twice as large as the bulk value.