Enhancement of torque efficiency and spin Hall angle driven collaboratively by orbital torque and spin-orbit torque

Spin-orbit torque (SOT) has been extensively applied to magnetization manipulation in low power consumption logic and memory devices. However, it is believed that materials with strong spin-orbit coupling (SOC) are indispensable for magnetic torque generation. Recently, theoretical studies have indicated that the oxides of light materials with weak SOC can provide a sizable orbital torque (OT), inducing magnetization switching. Here, we experimentally report the extreme enhancement of torque efficiency and spin Hall angle through the natural oxidation of Cu with weak SOC in the perpendicularly magnetized Pt/Co/Cu-CuOx multilayers. The values of torque efficiency and spin Hall angle increase by approximately five times by tuning the surface oxidation at room temperature. The comparative analysis of the effective field reveals that the significant enhancement mainly originates from the collaborative drive of the OT at the Cu/CuOx interface and the SOT from the Pt layer. This finding provides a powerful way to engineer the high-efficient spintronic devices through combining OT and SOT to improve the torque efficiency. Published under an exclusive license by AIP Publishing.