Spin diffusion length associated with out-of-plane conductivity of Pt in spin pumping experiments

We present a broadband ferromagnetic resonance study of the Gilbert damping enhancement ($\Delta \alpha$) due to spin pumping in NiFe/Pt bilayers. The bilayers, which have negligible interfacial memory loss, are studied as function Pt layer thickness ($t_{\text{Pt}}$) and temperature (100-293 K). Within framework diffusive theory, we demonstrate that Dyakonov-Perel (DP) or Elliot-Yaffet (EY) relaxation mechanisms acting alone incompatible with our observations. In contrast, if consider relation between characteristic time ($\tau_{\text{s}}$) momentum ($\tau_{\text{p}}$) is determined by superposition DP EY mechanisms, qualitative quantitative agreement experimental results excellent. Remarkably, found $\tau_{\text{p}}$ must be out-of-plane electrical resistivity ($\rho$) film hence its diffusion length ($\lambda_{\text{Pt}}$) independent $t_{\text{Pt}}$. Our work settles controversy regarding $t_{\text{Pt}}$ dependence $\lambda_{\text{Pt}}$ demonstrating fundamental connection $\rho$ considered along same direction current flow. \end{abstract}