Strong Spin Pumping in Permalloy-Iridium Heterostructures

We report a study of spin pumping in Permalloy/iridium (Py/Ir) and Py/Cu/Ir heterostructures as a function of Ir thickness. Ir is shown to be a strong spin sink, leading to enhancements of the Gilbert damping parameter of 50% and 170% with and without the Cu interlayer, respectively. Our results are consistent with strong spin-memory loss at the interface with Ir. The thickness dependence of the damping parameter in Py/Ir is exponential in nature, suggesting that no magnetic proximity effect exists. The combination of a strong spin-mixing conductance without magnetic proximity effect may make Ir a strong candidate for studies and devices related to spin Hall effects.