Enhanced Field-Like Torque Generated from the Anisotropic Spin-Split Effect in Triple-Domain RuO2 for Energy-Efficient Spin–Orbit Torque Magnetic Random-Access Memory

Abstract

Spin-current generation via the anisotropic spin-split effect has been predicted in antiferromagnetic RuO₂, where the symmetry of RuO₂ plays a critical role in spin–orbit torque (SOT). This phenomenon has garnered attention for its potential to enable energy-efficient spintronic devices, such as SOT magnetic random-access memory. In this study, a high-quality RuO₂ (100) epitaxial film with a well-controlled triple-domain-structure is analyzed, and it is confirmed that out-of-plane spin-current generation is independent of the Néel vector ($\vec{N}$). This $\vec{N}$ independence of the out-of-plane spin current leads to equal SOT values for the two orthogonal currents. The spin-split effect-induced SOT demonstrates a field-like (FL) torque efficiency (−0.066 ± 0.001) that is six times higher than that of the Slonczewski-like torque efficiency (−0.011 ± 0.001). Furthermore, micromagnetic simulations show that this high FL torque reduces the critical switching voltage by a factor of 2.6 in the sub-nanosecond regime in an SOT device. These findings contribute to advancing research and the development of highly energy-efficient antiferromagnetic-based SOT magnetic random-access memory.