(a) Position-sensitive area-detector image of the (qx, qz) unpolarized neutron scattering, with polarized traces along (b) the specular (qx=0) and (c) the first off-specular (qx=3.6 μm−1) reflections. The fitted depth-dependent nuclear (ρΝ, solid black and dashed blue curves) and magnetic (ρΜ, solid red and dashed green curves) scattering densities from the specular measurement are shown in (d), over the protected film (dashed curves) and the vortex region (solid curves). On top of the Si substrate (yellow region), at increasing depth, the film structure corresponds to the Pd seed (grey), Co/Pd underlayer (pink), Co dot (blue), Ta cap (green) and air (white). The calculated reflectivity from these depth profiles are shown as solid lines in (b). The Born-simulated reflectometry patterns from the OOMMF simulations are shown as dashed lines in (b) and (c). Error bars in qz identify machine precision; error bars in normalized reflectivity are defined by the s.d. and scale with the square root of the number of measurements.