Search for: All records

We measure spin-orbit torque generated by exfoliated layers of the low-symmetry semi-metal ZrTe3 using the spin-torque ferromagnetic resonance (ST-FMR) technique. When the ZrTe3 has a thickness greater than about 10 nm, artifacts due to spin pumping and/or resonant heating can cause the standard ST-FMR analysis to overestimate the true magnitude of the torque efficiency by as much as a factor of 30, and to indicate incorrectly that the spin-orbit torque depends strongly on the ZrTe3 layer thickness. Artifact-free measurements can still be achieved over a substantial thickness range by the method developed recently to detect ST-FMR signals in the Hall geometry as well as the longitudinal geometry. ZrTe3/Permalloy samples generate a conventional in-plane anti-damping spin torque efficiency ξDL|| = 0.014 ± 0.004, and an unconventional in-plane field-like torque efficiency |ξFL||| = 0.003 ± 0.001. The out-of-plane anti-damping torque is negligible. We suggest that artifacts similarly interfere with the standard ST-FMR analysis for other van der Waals samples thicker than about 10 nm. 

Spin‐orbit torques generated by exfoliated layers of the low‐symmetry semi‐metal ZrTe₃are measured using the spin‐torque ferromagnetic resonance (ST‐FMR) technique. When the ZrTe₃has a thickness greater than about 10 nm, artifacts due to spin pumping and/or resonant heating can cause the standard ST‐FMR analysis to overestimate the true magnitude of the torque efficiency by as much as a factor of 30, and to indicate incorrectly that the spin‐orbit torque depends strongly on the ZrTe₃layer thickness. Artifact‐free measurements can still be achieved over a substantial thickness range by the method developed recently to detect ST‐FMR signals in the Hall geometry as well as the longitudinal geometry. ZrTe₃/Permalloy samples generate a conventional in‐plane anti‐damping spin torque efficiency = 0.014 ± 0.004, and an unconventional in‐plane field‐like torque efficiency = 0.003 ± 0.001. The out‐of‐plane anti‐damping torque is negligible. It is suggested that artifacts similarly interfere with the standard ST‐FMR analysis for other van der Waals samples thicker than about 10 nm.

 

Spin–orbit torques generated by a spin current are key to magnetic switching in spintronic applications. The polarization of the spin current dictates the direction of switching required for energy‐efficient devices. Conventionally, the polarizations of these spin currents are restricted to be along a certain direction due to the symmetry of the material allowing only for efficient in‐plane magnetic switching. Unconventional spin–orbit torques arising from novel spin current polarizations, however, have the potential to switch other magnetization orientations such as perpendicular magnetic anisotropy, which is desired for higher density spintronic‐based memory devices. Here, it is demonstrated that low crystalline symmetry is not required for unconventional spin–orbit torques and can be generated in a nonmagnetic high symmetry material, iridium dioxide (IrO₂), using epitaxial design. It is shown that by reducing the relative crystalline symmetry with respect to the growth direction large unconventional spin currents can be generated and hence spin–orbit torques. Furthermore, the spin polarizations detected in (001), (110), and (111) oriented IrO₂thin films are compared to show which crystal symmetries restrict unconventional spin transport. Understanding and tuning unconventional spin transport generation in high symmetry materials can provide a new route towards energy‐efficient magnetic switching in spintronic devices.