Amplifying Spin-Orbit Torque Efficiency via a Crystallographic Approach

Currently, transition-metal-oxide based spintronics have sparked a tremendous research interests thanks to their non-trivial properties in solid-state physics and soon become potential candidates to participate into the spin-orbit torque (SOT) technology in the third generation of magnetoresistive random access memory.Recent studies have highlighted the ability of epitaxially grown SrIrO₃ to generate a spin current with remarkable charge-to-spin conversion efficiency. However, a comprehensive study of crystallographic dependence of SOT effect in single crystal SrIrO₃ thin films remains lacking.To address this gap, we prepare SrIrO₃(001)/La_0.7Sr_0.3MnO₃(001) epitaxial bilayers on the SrTiO₃ single crystal substrates by using pulsed laser deposition technique. The SrIrO₃ layer serves as a spin generator with orthorhombic symmetry, facilitating the study of anisotropic SOT effects, while LSMO functions as a ferromagnetic layer with in-plane magnetic isotropy for spin detection. Employing a loop-shift method on Hall bar devices with different crystallographic orientations, we observed that applying current along the [110] direction of SrIrO3 resulted in nearly five times higher SOT efficiency compared to applying current along the [100] direction, as indicated by the peak shift (<i>H_eff</i>) relative to the sensing current amplitude. This outcome reveals a robust correlation between the crystal structure and the SOT effects, offering an ideal platform for manipulating SOT properties in TMO-based spintronic devices.