Temperature-dependent spin scattering in Pt and at its interfaces

Pt is an important material for spintronic devices, as it exhibits a significant spin Hall effect, enabling its applications as an efficient source of spin currents. Among key parameters describing spin-transport properties are the spin diffusion length (SDL) and the interfacial spin-scattering $\delta $. The reported values of SDL in Pt range from 0.5 to 15nm, likely due to the differences in the measurement approaches and material purity. Little is presently known about $\delta $. We utilized current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) and magnetic nanopillar structures to determine the dependence of $\delta $ and SDL in Pt on temperature T. Both $\delta $ and SDL increase by almost a factor of two between 300K and 7K, implying that the bulk spin scattering decreases while the interfacial spin scattering increases with decreasing T. These opposite trends result in a nonmonotonic dependence of GMR on T for thin Pt layers. We discuss the possible mechanisms for the unexpected dependence of $\delta $ on T. We also show that the SDL is within a factor of 2 of the mean free path, implying that almost every scattering event is spin flipping. This result provides a simple approach to estimate SDL in Pt and other materials with strong spin-orbit interaction.