title: Spin Torque Study of the Spin Hall Conductivity and Spin Diffusion Length in Platinum Thin Films with Varying Resistivity.
abstract: We report measurements of the spin torque efficiencies in perpendicularly magnetized Pt/Co bilayers where the Pt resistivity ρ_{Pt} is strongly dependent on thickness t_{Pt}. The dampinglike spin Hall torque efficiency per unit current density ξ_{DL}^{j} varies significantly with t_{Pt}, exhibiting a peak value ξ_{DL}^{j}=0.12 at t_{Pt}=2.8-3.9  nm. In contrast, ξ_{DL}^{j}/ρ_{Pt} increases monotonically with t_{Pt} and saturates for t_{Pt}>5  nm, consistent with an intrinsic spin Hall effect mechanism, in which ξ_{DL}^{j} is enhanced by an increase in ρ_{Pt}. Assuming the Elliott-Yafet spin scattering mechanism dominates, we estimate that the spin diffusion length λ_{s}=(0.77±0.08)×10^{-15}  Ω·m^{2}/ρ_{Pt}.
authors.affiliation: Cornell University, Ithaca, New York 14853, USA.
authors.forename: Minh-Hai
authors.initials: MH
authors.lastname: Nguyen
authors.affiliation: Cornell University, Ithaca, New York 14853, USA.|Kavli Institute at Cornell, Ithaca, New York 14853, USA.
authors.forename: D C
authors.initials: DC
authors.lastname: Ralph
authors.affiliation: Cornell University, Ithaca, New York 14853, USA.
authors.forename: R A
authors.initials: RA
authors.lastname: Buhrman