Highly efficient charge-to-spin conversion from in situ Bi2Se3/Fe heterostructures

Topological insulators (TIs) show bright prospects in exerting spin–orbit torques (SOTs) and inducing magnetization switching in the adjacent ferromagnetic (FM) layer. However, a variation of the SOT efficiency values may be attributed to the ex situ deposition of the FM layer or the complex capping/decapping processes of the protection layer. We have employed an in situ fabrication of Bi2Se3/Fe heterostructures and investigated the SOT efficiency by spin torque ferromagnetic resonance. An enhanced SOT efficiency and large effective spin mixing conductance have been obtained especially below 100 K as compared with ex situ methods. The enhancement of the SOT efficiency is attributed to a much thinner interfacial layer (0.96 nm) in the in situ case and thus the enhanced interface spin transparency. Our results reveal the crucial role of interface engineering in exploring highly efficient TI-based spintronic devices.