Large Interfacial Rashba Interaction Generating Strong Spin–Orbit Torques in Atomically Thin Metallic Heterostructures

[Image: see text] The hallmark of spintronics has been the ability of spin–orbit interactions to convert a charge current into a spin current and vice versa, mainly in the bulk of heavy metal thin films. Here, we demonstrate how a light metal interface profoundly affects both the nature of spin–orbit torques and its efficiency in terms of damping-like (H(DL)) and field-like (H(FL)) effective fields in ultrathin Co films. We measure unexpectedly H(FL)/H(DL) ratios much larger than 1 by inserting a nanometer-thin Al metallic layer in Pt|Co|Al|Pt as compared to a similar stacking, including Cu as a reference. From our modeling, these results evidence the existence of large Rashba interaction at the Co|Al interface generating a giant H(FL), which is not expected from a metallic interface. The occurrence of such enhanced torques from an interfacial origin is further validated by demonstrating current-induced magnetization reversal showing a significant decrease of the critical current for switching.