High-efficient spin injection in Co/GeSn with ferromagnetic resonance driven spin pumping

Abstract

Germanium tin (GeSn) is one of the candidates for spintronic materials owing to its tunable spin–orbit interaction and barrier height with increasing the Sn content. However, as a potential spintronic material, its spin related properties have not been fully understood yet. We investigate the efficiency of spin current detection in GeSn by using the technique of ferromagnetic resonance drive spin pumping. Some fundamental spintronic parameters can be extracted from our experimental results to measure the change of spin injection/conversion efficiency. A Co layer is deposited on the top GeSn thin films to serve as the spin current generator. Here, the effective spin mixing conductance (geff↑↓) and the product of spin diffusion length and spin Hall angle [λsθISHE(%)] represent the spin injection efficiency and the spin-charge conversion efficiency, respectively. geff↑↓ and λsθISHE(%) are 9.3 × 1019 m−2 and 1.39 nm for p-type GeSn; and 7.4 × 1019 m−2 and 2.09 nm for n-type GeSn. The high-efficient spin injection in both p-type and n-type Co/GeSn systems is attributed to a low barrier height at the Co/GeSn interface because the spin current at the interface is proportional to the square root of barrier height. Our experimental results show that GeSn is effective as a spin current sink.