Symmetry Control of Unconventional Spin-Orbit Torques in IrO 2 .

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, we demonstrate that low crystalline symmetry is not required for unconventional spin-orbit torques and can be generated in a non-magnetic high symmetry material, iridium dioxide (IrO 2 ), using epitaxial design. We show by reducing the relative crystalline symmetry with respect to the growth direction we can generate large unconventional spin currents and hence spin-orbit torques. Furthermore, we compare the spin polarizations detected in (001), (110), and (111) oriented IrO 2 thin films 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. This article is protected by copyright. All rights reserved.