A toggle MRAM bit modeled in Verilog-A

A physically-based behavioral model for a toggle mode magnetic random access memory (MRAM) cell, developed in Verilog-A is presented. The model describes the magnetic behavior of two single-domain, magnetic free-layers coupled through exchange and magnetostatic interactions. The model also includes spin-dynamic effects. The external interface to the model is electrical in nature, consisting of input currents on the word and bit lines and an output in the form of a magnetoresistance based on the orientation of one of the free layers. The model faithfully reproduces toggling of the magnetic state (reversal of magnetization directions of the two layers through an intermediate spin flop state) in response to a conventional box field stimulus. The model will facilitate the design and analysis of complex spintronic or hybrid spintronic–electronic circuits in a simulation environment that is familiar to most circuit designers.