Spin-Transfer Torque Magnetic Tunnel Junction Model Based on Fokker-Planck Equation for Stochastic Circuit Simulations

A spin-transfer torque magnetic tunnel junction (STT-MTJ) model is proposed which is based on Fokker-Planck equation and described by Verilog-A for stochastic circuit simulations by SPICE. A new framework to calculate the magnetization angle makes the model usable widely in STT-MT J applications. The model can be applied to general situations in which the electrical current flowing through an MTJ changes its strength and direction in time. The CPU time for simulation of a large-scale circuit is shown to be much shorter than the model which is based on stochastic Landau-Lifshitz-Gilbert-Slonczewsky (s-LLGS) equation with a Langevin field. The model is applied to a leaky integrate-and-fire (LIF) neuron circuit for spiking neural networks (SNNs).