Cu-Based Non-Local Spin Valves*

As microelectronic components scale down, new materials must be used to mitigate the negative effects of size reduction, such as increasing resistivity in interconnects. One promising material in this regard is the ordered metallic alloy θ-phase Al₂Cu. With growing interest in spintronic devices, including for interconnect applications, it is important to understand not only charge transport in such materials, but also spin transport. There is a complete dearth of knowledge and understanding of spin transport in light-metal alloys, however, despite their potential to outperform metals such as Al. We address this here through the first study of ordered-alloy-based all-metallic non-local spin valves, focusing on θ-Al₂Cu. X-ray diffraction confirms the formation of 112-oriented polycrystalline θ-Al₂Cu films which we have optimized via thickness, composition, and post-deposition annealing. Optimized films have been incorporated in non-local spin valves, enabling temperature-dependent measurements of the spin signal and θ-Al₂Cu spin diffusion length. Elliot-Yafet spin relaxation probabilities are found to be close to those of Al, much improved over Cu, and with no evidence of Kondo spin relaxation. This suggests promise for the incorporation of θ-Al₂Cu in metallic spin transport devices.