Switching perpendicular magnets for Processing-in-memory with voltage gated Weyl Semimetals

Abstract

Processing-in-memory (PIM) reduces data transfer latency by rolling memory and logic elements into one compute location. As an emergent material candidate for such an architecture, we propose a strained Weyl semimetal based spin-orbit-torque random-access memory (SWSM-SOTRAM) device. The spin-orbit torque (SOT) originates from two mechanisms: (1) the inverse spin Galvanic effect (iSGE), which generates nonequilibrium in-plane spin accumulation at interfaces, and (2) a bulk spin Hall effect (SHE), which produces a transverse spin current carrying out-of-plane spin angular momentum. The latter is tunable via an exchange Zeeman field. Both effects are evaluated using the tight-binding model coupled with a nonequilibrium Green's function (TB-NEGF) formalism for quantum transport. Information write is achieved through SOT switching of an out-of-plane free magnet. A piezo attached to a magnetostrictive selector modulates the strain in the latter, leading to the rotation of the magnetization and hence the exchange Zeeman field exerted on the Weyl semimetal. This strain-controlled exchange field enables the symmetry tuning of the Weyl semimetal and modulation of its spin Hall effect. The TB-NEGF calculations of SHE and iSGE, combined with Landau-Lifshitz-Gilbert (LLG) simulations of magnetization dynamics, establish the SOT switching mechanism and demonstrate a pathway toward the SWSM-SOTRAM PIM device.