Amplifying spin-orbit torque efficiency via a crystallographic approach
Chi-Yen Huang1*, Yi-Yu Cheng1, Chun-Chieh Hsu1, Yi-Ting Lee1, Yen-Lin Huang1, Chao-Yao Yang1
1Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
* Presenter:Chi-Yen Huang, email:yenh98355@gmail.com
Currently, transition-metal-oxide (TMO)-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. Epitaxially grown SrIrO₃ had been found capable of generating a spin current with a remarkable charge-to-spin conversion efficiency in the recent studies. However, none of the studies comprehensively explored the correlation between the crystal structure and the associated SOT effect, namely, the SOT anisotropy in an SrIrO₃ crystal. To address this issue, an SrIrO₃(001)/La₀₇Sr₀₃MnO₃(001) (LSMO) epitaxial bilayer on an SrTiO₃ single crystal substrate was prepared by using a pulse laser deposition (PLD) technique, in which SrIrO₃ is a spin generator with an orthorhombic symmetry to enable the study of the anisotropic SOT effect and LSMO is a ferromagnetic layer with an in-plane anisotropy for spin detection. We conducted a loop-shift method on Hall bar devices with different crystallographic orientations, as shown in Fig. 1. It has been shown applying the current along the [110] direction of SrIrO₃ would yield a higher SOT efficiency than applying the current along [100] direction, in terms of the peak shift (Heff) as a function of the sensing current amplitude, nearly 5-fold as shown in Fig. 2. The result reveals a strong correlation between the crystal structure and the SOT effect, providing an ideal playground to manipulate the SOT properties in a TMO-based spintronic device.
Keywords: Transition metal oxide, Spintronics, Spin-orbit torque, Epitaxial, Loop-shift method