Unidirectional orbital magnetoresistance in light-metal–ferromagnet bilayers

We report the observation of a unidirectional magnetoresistance (UMR) that originates from nonequilibrium orbital momentum induced by an electric current in naturally oxidized Cu/Co bilayer. The orbital-UMR scales with torque efficiency due to Rashba-Edelstein effect upon changing Co thickness and temperature, reflecting their common origin. attribute UMR orbital-dependent electron scattering orbital-to-spin conversion ferromagnetic layer. In contrast spin-current UMR, magnon contribution is absent thin layers, which we ascribe lack coupling between low energy magnons current. emerges layers thicker than about 5 nm, comparable length. Our results provide insight into transfer processes relevant for optimization spintronic devices based on light metals transport.