A Physics-Based Compact Model of Stochastic Switching in Spin-Transfer Torque Magnetic Memory

Spin-transfer torque random-access memory (STT-RAM) is gainingmomentum as a promising technology for high-density and embedded nonvolatile memory. Owing to random thermal fluctuations, switching transitions generally display statistical variations from cycle to cycle. Stochasticvariations are critical to thehinderingofmemory and computing applications of STT-RAM. To enable the design of STT-RAM circuits for memory and computing, there is a need for accurate compact models capable of predicting the stochastic behavior. Here, we present a detailed model accounting for the anomalous thermal regime of switching deviating fromthe Neel-Brown thermalmodel below 200 ns. Anomalous switching is explainedby the nonlinear lowering of the energybarrier associatedwith the perpendicular magnetic anisotropy (PMA). The model is extensively verified against the write-error-rate (WER) data as a function of applied voltage and pulsewidth and experimental switching time-delay distributions.