Perpendicular magnetic anisotropy in ultrathin Co|Ni multilayer films studied with ferromagnetic resonance and magnetic x-ray microspectroscopy

► We show record sensitivity of x-ray microscopy in a 1 nm Co effective thickness. ► We found extreme sensitivity of the domain structure to number of bilayer repeats. ► Perpendicular anisotropy is nearly independent of the number of bilayers. ► We have combined Ferromagnetic resonance and high resolution XMCD microscopy.