Spin-reorientation transition in Co ∕ Pt multilayers on nanospheres

Co/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 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.