Effect of asymmetric Pt thickness on the inverse spin Hall voltage in Pt/Co/Pt trilayers

Ferromagnetic resonance (FMR) is an effective technique for probing the magnetization dynamics of magnetic thin films. In particular, bilayer systems composed of a paramagnetic layer and a ferromagnetic layer are commonly used for FMR-driven spin pumping experiments. Spin pump-and-probe models have been adopted to obtain the spin Hall angle (theta(SHE)) and spin diffusion length (lambda(N)) for various single layer and bilayer systems. Trilayer systems, however, have rarely been studied with the same model. In this work, we study the structural asymmetry effect on Pt/Co/Pt trilayers and find that the different thicknesses of Pt on two sides of Co may change the spin current sign. Furthermore, we propose a method that allows analysis of Pt/Co/Pt trilayers using the spin pump-and-probe model. The obtained values of theta(Pt) and lambda(Pt) in the Pt/Co/Pt system are 0.116 nm and 1.15 nm, respectively, which are consistent with the values obtained from other Pt-based bilayer systems.