Micromagnetic Analysis of Statistical Switching in Perpendicular Magnetic Tunnel Junctions with Double Reference Layers

The recent technological realization of perpendicular magnetic tunnel junction (MTJ) with two reference layers has opened a new route for scaling the overall size of spin-transfer torque MRAM. This is because for an antiparallel configuration of the magnetization of the reference layers the two spin-transfer torques add each other constructively giving rise to more efficient switching processes of the free layer magnetization as compared to a single MTJ. In this Letter, we use full micromagnetic simulations to study the magnetization switching of a double magnetic tunnel junction. Our results show that probability distribution function (PDF) of the switching time is the same for both switching processes (parallel to antiparallel and vice versa) and the PDF approaches a Gaussian shape for switching time smaller than 1ns. We also find out that the dynamical performance (achieved for switching time below 1ns) of double magnetic tunnel junctions with circular shape and diameter ranging from 30 to 14 nm are comparable. In addition, compared to full micromagnetic data computations of the PDF computed within the macrospin approximation show an overestimation of the skewness for MTJ with circular shape and diameter of 30nm and 20nm while they are very close for 14 nm in diameter as expected. The PDF comparison can drive the design of CMOS hybrid system consider the proper micromagnetic model.