Observation of the nonlocal spin-orbital effective field

The spin-orbital interaction in heavy nonmagnetic metal/ferromagnetic metal bilayer systems has attracted great attention and exhibited promising potentials in magnetic logic devices, where the magnetization direction is controlled by passing an electric current. It is found that the spin-orbital interaction induces both an effective field and torque on the magnetization, which have been attributed to two different origins: the Rashba effect and the spin Hall effect. It requires quantitative analysis to distinguish the two mechanisms. Here we show sensitive spin-orbital effective field measurements up to 10 nm thick ferromagnetic layer and find the effective field rapidly diminishes with the increase of the ferromagnetic layer thickness. We further show that this effective field persists even with the insertion of a copper spacer. The nonlocal measurement suggests that the spin-orbital effective field does not rely on the heavy normal metal/ferromagnetic metal interface.