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

Abstract

We have measured the size effect in nonlocal Gilbert relaxation rate in FM(t${}_{FM}$) / Cu (5nm) [/ Pt (2nm)] / Al(2nm) heterostructures, FM = \{ Ni${}_{81}$Fe${}_{19}$, Co${}_{60}$Fe${}_{20}$B${}_{20}$, pure Co\}. Common behavior is observed for three FM layers, where the additional relaxation obeys both a strict inverse power law dependence $\Delta G=K{t}^n$, $n=-\text{1.04}\pm \text{0.06}$ and a similar magnitude $K=\text{224}\pm \text{40 Mhz}\cdot \text{nm}$. As the tested FM layers span an order of magnitude in spin diffusion length ${\lambda }_{SDL}$, the results are in support of spin diffusion, rather than nonlocal resistivity, as the origin of the effect.