$\mathrm{Co}∕\mathrm{Pt}$ multilayers have been deposited onto self-assembled arrays of spherical particles. The radial film thickness variation changes both the magnitude and direction of the magnetic anisotropy within a single cap. By adjusting the thickness of the Co layers, we produced caps that exhibit a reorientation of the magnetization from in plane at the center toward out of plane at the rim within a distance of less than $100\mathrm{nm}$. The domain configuration and its reversal behavior in applied magnetic fields were studied with high spatial resolution scanning transmission x-ray microscopy, providing quantitative insight into nanoscale magnetism.

• Received 10 March 2008

DOI:https://doi.org/10.1103/PhysRevB.77.134415