Dynamic Skyrmion-Mediated Switching of Perpendicular MTJs: Feasibility Analysis of Scaling to 20 nm With Thermal Noise

One method of creating and annihilating skyrmions in confined geometries is to use voltage-controlled magnetic anisotropy (VCMA). The previous study shows that robust voltage-controlled ferromagnetic reversal from “up” to “down” state in the soft layer of a perpendicular magnetic tunnel junction (p-MTJ) can be achieved by creating and subsequently annihilating an intermediate skyrmion state in the presence of room temperature thermal noise and anisotropy variation across grains. However, when scaling to 20 nm, thermal noise can annihilate the skyrmions, for example, by randomly moving the core toward the boundary of the nanostructure. In this work, we study three p-MTJs of different dimensions, specifically lateral dimensions of 100, 50, and 20 nm and investigate the change in switching behavior as the dimension is decreased. In particular, we show that while skyrmion-mediated switching of ferromagnets in the presence of thermal perturbation is feasible down to lateral dimensions ~20 nm, the large values of VCMA and Dzyaloshinskii-Moriya interaction (DMI) needed at ~20 nm lateral dimensions have only been theoretically predicted and are yet to be experimentally demonstrated to date.