A Comparative Study between Spin-Transfer-Torque (STT) and Spin-Hall-Effect (SHE) Switching Mechanisms in PMTJ using SPICE

Spin transfer torque magnetoresistive random access memory (STT-MRAM) is the leading candidate for spinbased memories. Nevertheless, the high write energy and read disturbance of STT-MRAM motivated researchers to find other solutions. Spin Hall effect (SHE) based MRAM is an alternative for STT-MRAM which also provides non-volatility, zero leakage, and competitive area per bit, but with a lower write current. This work focuses on a systematic performance analysis of these two proposed memory solutions. SHE requires an external field to deterministically switch perpendicular magnetic anisotropy (PMA) MTJ. A previous experiment showed SHE can switch composite MTJ containing an in-plane layer without any field. In this work, both traditional and composite MTJ structures are modeled in SPICE which can reproduce realistic MTJ characteristics with user-defined input parameters. This selfcontained model is used to compare the write energy and delay of STT-MRAM and SHE-MRAM for various write schemes including thermal fluctuation. Our simulations show, compared to STT-MRAM, SHE-MRAM improves the write delay and energy by 8× and 7×, respectively. Based on our extensive analysis incorporating the latest advances in magnetic materials and device technology, we predict that SHE-MRAM is a feasible low energy memory solution for future computing systems.