Hybrid Spin-Orbit Torque/Spin-Transfer Torque-Based Multibit Cell for Area-Efficient Magnetic Random Access Memory

Spin-orbit torque (SOT) devices for magnetic random access memory (MRAM) are promising due to their higher endurance, faster switching speed, and higher energy efficiency compared to the spin-transfer torque (STT) devices. However, the SOT-MRAM’s areal density is approximately half that of STT-MRAM, thereby mitigating its advantage. In this study, we propose a hybrid SOT–STT-based MRAM cell design that combines the favorable features of both the STT and the SOT devices. The hybrid SOT–STT memory cell integrates two bits within a single memory device, employing both STT and SOT mechanisms to write information in the two bits. Notably, the hybrid SOT–STT memory cell achieves twice the areal density of the SOT memory cells. Furthermore, it demonstrates approximately three times lower write energy and is 2.7 times faster compared to the STT-MRAM devices. By leveraging the desirable characteristics of SOT and STT memory, the hybrid memory design enables high-density and energy-efficient nonvolatile spin memory.