Self-consistent determination of spin Hall angle and spin diffusion length in Pt and Pd: The role of the interface spin loss

摘要

Spin Hall angle (θSH) and spin diffusion length (λsd) are the key parameters in describing the spin-charge conversion, which is an integral part of spintronics. Despite their importance and much effort devoted to quantifying them, significant inconsistencies in the reported values for the same given material exist. We report a self-consistent method to quantify both θSH and λsd of nonmagnetic materials by spin pumping with various ferromagnetic (FM) pumping sources. We characterize the spin-charge conversion for Pt and Pd with various FM combinations using (i) effective spin-mixing conductance, (ii) microwave photoresistance, and (iii) inverse spin Hall effect measurements and find that the pumped spin current suffers an interfacial spin loss (ISL), whose magnitude varies for different interfaces. By properly treating the ISL effect, we obtained consistent values of θSH and λsd for both Pt and Pd regardless of the ferromagnet used.