Current-induced spin–orbit field in permalloy interfaced with ultrathin Ti and Cu

Abstract

How spin–orbit torques emerge from materials with weak spin–orbit coupling (e.g., light metals) is an open question in spintronics. Here, we report on a field-like spin–orbit torque (i.e., in-plane spin–orbit field transverse to the current axis) in SiO2-sandwiched Permalloy (Py), with the top Py-SiO2 interface incorporating ultrathin Ti or Cu. In both SiO2/Py/Ti/SiO2 and SiO2/Py/Cu/SiO2, this spin–orbit field opposes the classical Oersted field. While the magnitude of the spin–orbit field is at least a factor of 3 greater than the Oersted field, we do not observe evidence for a significant damping-like torque in SiO2/Py/Ti/SiO2 or SiO2/Py/Cu/SiO2. Our findings point to contributions from a Rashba-Edelstein effect or spin–orbit precession at the (Ti, Cu)-inserted interface.