Dependence of nonlocal Gilbert damping on the ferromagnetic layer type in ferromagnet/Cu/Pt heterostructures

We have measured the size effect in the nonlocal Gilbert relaxation rate in ferromagnet (FM) (tFM)/Cu(3nm)[/Pt(2nm)]/Al(3nm) heterostructures, FM={Ni81Fe19,Co60Fe20B20,pureCo}. A common behavior is observed for three FM layers where the additional relaxation obeys both a strict inverse power law dependence ΔG=Ktn, n=−1.04±0.06 and a similar magnitude K=224±40MHz⋅nm. As the tested FM layers span an order of magnitude in spin diffusion length λSD, the results are in support of spin diffusion rather than nonlocal resistivity as the origin of the effect.