Seed influence on the ferromagnetic resonance response of Co/Ni multilayers

The effect of Pd and Ru seed layers on the magnetic properties of [Co/Ni](N) multilayers with varying number of bilayer repeats N is investigated using vector network analyzer ferromagnetic resonance. The effective anisotropy field H-Keff is found to increase with N for Ru seed, but decreases for Pd until N - 15. As N is increased beyond 15, H-Keff decreases for both seeds. In contrast, the damping parameter alpha decreases with N regardless of the seed, showing a 1/N dependence. Taking spin pumping into account, the intrinsic damping alpha(0) for both Pd and Ru seeds reduce to alpha(0) approximate to 0.01. These results demonstrate that there can be a strong influence of the seed/Co interface on anisotropy, especially for sufficiently low N, but not necessarily on alpha(0). (C) 2014 AIP Publishing LLC.