Novel Operation of a Multi-Bit SOT Memory Cell Addressed With a Single Write Line

Spin-orbit torque (SOT) originates from the spin-orbit interaction of non-magnetic heavy metals (HMs), allowing for an electrical manipulation of perpendicular magnetization in HM/ferromagnet (FM)/oxide structures. In this paper, we experimentally demonstrate the SOT-induced switching of two FM bits addressed with a single write line. We fabricate a device consisting of two perpendicularly magnetized Ta/CoFeB/MgO structures with a common Ta underlayer, in which the magnetization directions of the two FM bits could be concurrently controlled by injecting a single current pulse. This suggests that multiple bits in SOT-based devices can be written as either “0” or “1” at the same time. Moreover, the selective switching of a specific bit is achieved by differentiating the critical switching currents between the two FM bits, which is crucial in demonstrating multi-level cell SOT memory. Our results provide an efficient writing mechanism, enabling wider applications of SOT-based spintronic devices.