A modular spin-circuit model for magnetic tunnel junction devices

We introduce a modular, physics-based, spin-circuit SPICE model to analyze conventional (charge-voltage driven) and next-generation (spin-voltage driven) Magnetic Tunnel Junctions (MTJ) in a unified circuit framework. Proposed model has 3 important novelties: (1) Quantitatively matches representative experiments for charge-driven (c-MTJ) [1,2] and spin-driven MTJ (s-MTJ) devices [3], by solving transport equations and magnetization dynamics, linking experiments directly to circuits, (2) through benchmarked circuit modules against experiments and theory [4], covers a wide range of transport and magnet phenomena, including detailed spin-transfer-torque (STT) physics at interfaces (SMR due to Giant Spin Hall Effect) [5], thermal noise in magnets, magnetic interactions between magnets as well as voltage-dependent spin-torque and TMR of MTJ devices. (3) provides circuit metrics such as Energy-Delay product [6] by capturing non-idealities including spin-absorption efficiency at the GSHE-FM interface, high-bias features of TMR and STT of the MTJs, bridging material parameters to circuit metrics. The modularity of our framework allows a "plug-and-play" approach to add or subtract different phenomena that are derived from a diverse set of underlying theories (spin-diffusion, quantum transport, magnetization dynamics through Landau-Lifshitz-Gilbert (LLG) equation to achieve the desired level of complexity for modeling MTJ devices. Due to these reasons, we believe our model stands out compared to others in terms of flexibility, extensibility, close connection to material parameters and depth of physics captured and is the best candidate TCAD model for the STT-MRAM industry.