Properties of Ni/Co multilayers as a function of the number of multilayer repetitions

We study the static and dynamic properties of magnetic multilayers with perpendicular magnetic anisotropy (PMA) composed of alternating ultrathin layers of Co and Ni. In particular, the evolution of PMA and the Gilbert damping parameter is investigated as a function of thickness using ferromagnetic resonance. We find a rather small Gilbert damping constant α = 0.014 which is almost independent of the number of multilayer repetitions. In addition, the out-of-plane angular dependence of the resonance fields can only be explained when a second order term for the uniaxial out-of-plane anisotropy is included in the energy density.