Observation of a non-trivial in-plane field-like torque due to out-of-plane spin polarization in Al/Ni80Fe20/AlOx heterostructures.

We performed spin-torque ferromagnetic resonance studies on the Al/NiFe/AlOx heterostructure. We observed a large non-trivial field-like torque, τ FL z , due to the out-of-plane spin polarization, despite the lack of heavy metal in our multilayer. The torque conductivity is found to be significant with a value equal to σ FL z = (21 ± 2) ℏ 2 e × 10 3 Ω − 1 m − 1 . From a detailed Al thickness dependence, we show that τ FL z arises from the interface between Al and NiFe. We demonstrate that the observed τ FL z arises from the spin-swapping mechanism at the Al/NiFe interface rather than the orbital Hall effect of Al. This observation of a non-trivial spin–orbit torque in the low-cost light element, Al, is highly significant for the energy-efficient control of spintronic devices. [ABSTRACT FROM AUTHOR]