Nonlocal spin transport in the light intermetallic alloy Al₂Cu

Transport of spin-polarized electrons injected into light metals is central to the function of numerous spintronic devices and is understood to be limited by Elliott-Yafet spin relaxation. Exploration and quantification of Elliott-Yafet spin relaxation in light metals has not advanced beyond a handful of elements, however, despite the exciting potential for long-range spin transport in alloys. Here, we present a detailed study of spin transport in nonlocal spin valves based on the promising intermetallic alloy Al₂Cu. X-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy, atomic force microscopy, and electronic transport confirm single-phase, textured, polycrystalline θ-Al₂Cu thin films, particularly after moderate annealing. Measurements on Co-Fe/Al₂Cu-based nonlocal spin valves (including the Hanle effect) then enable full quantification of spin relaxation parameters. The spin diffusion length in Al2Cu films is found to exceed 100 nm in the low-temperature limit, with Elliott-Yafet constants for phonon and defect scattering that significantly exceed those of Cu. These results are interpreted in light of density functional theory calculations considering spin relaxation hot spots, which also highlight other Al-Cu alloys of high potential interest. This work thus expands the quantitative study of spin transport and relaxation to alloys, laying the foundation for full exploration of light-metal alloys for long-range metallic spin transport.