Abstract
We study current-induced torques in /permalloy bilayers as a function of thickness. We measure the torques using both second-harmonic Hall and spin-torque ferromagnetic resonance techniques for samples with thicknesses that span from 16 nm down to a single monolayer. We confirm the existence of an out-of-plane antidamping torque, and we show directly that the sign of this torque component is reversed across a monolayer step in the . The magnitude of the out-of-plane antidamping torque depends only weakly on thickness, such that even a single-monolayer device provides a strong torque that is comparable to much thicker samples. In contrast, the out-of-plane fieldlike torque has a significant dependence on the thickness. We demonstrate that this fieldlike component originates predominantly from the Oersted field, thereby correcting a previous inference drawn by our group based on a more limited set of samples.
1 More- Received 10 July 2017
DOI:https://doi.org/10.1103/PhysRevB.96.054450
©2017 American Physical Society