Current-Induced Magnetization Switching in Light-Metal-Oxide/Ferromagnetic-Metal Bilayers via Orbital Rashba Effect

The orbital angular momentum (OAM) generation as well as its associated orbital torque is currently a matter of great interest in spin-orbitronics and is receiving increasing attention. In particular, recent theoretical work predicts that the oxidized light metal Cu can serve as an efficient OAM generator through its surface orbital Rashba effect. Here, for the first time, the crucial current-induced magnetic-field-free in-plane magnetization reversal is experimentally demonstrated in CoFeB/CuO_x bilayers without any heavy elements. We show that the critical current density can be comparable to that of strong spin-orbit coupling systems with heavy metals (Pt and Ta) and that the magnetization reversal mechanism is governed by coherent rotation in the grains through the second-harmonic and magneto-optical Kerr effect measurements. Our results indicate that light metal oxides can play an equally important role as heavy metals in magnetization reversal, broadening the choice of materials for engineering spintronic devices.