Study of Rashba Spin–Orbit Field at LaAlO₃/SrTiO₃ Heterointerfaces

Oxide interfaces such as LaAlO₃/SrTiO₃ (LAO/STO) are interesting platforms for the investigation of ‘spin–orbitronics’ because of their strongly coupled spin and orbital degrees of freedom due to the inversion asymmetry of the structure. In this investigation, we demonstrate a tunable Rashba spin–orbit field at the LAO/STO interface via the application of an external gate electric field. The strength of the Rashba field was indirectly estimated by measuring the planar angle dependence of the anisotropic magnetoresistance (AMR). The asymmetry of the planar AMR between θ = 0 and π indicates the existence of Rashba spin–orbit fields, which are tunable by adjusting the current density and gate electric field. From the AMR measurements, the effective Rashba field exhibits up to 4 T for the application of an external back-gate voltage of 30 V. This controllable and relatively high Rashba field suggests that the LAO/STO is an attractive 2-D interface for potential spin–orbitronic applications, such as spin-charge converters, spin-FETs, and spin–orbit torque devices.