Universal skyrmion logic gates and circuits based on antiferromagnetically coupled skyrmions without a topological Hall effect

Abstract

Nanoscale skyrmions are spin-based quasiparticles that are promising for nonvolatile logic applications. However, the presence of the skyrmion Hall effect (SkHE) in ferromagnetic skyrmions limits their performance in logic devices. Here, we present a detailed micromagnetic modeling study on low-energy skyrmion logic gate circuits based on skyrmions in synthetic antiferromagnetically coupled (SAF) metallic ferromagnetic layers to eliminate the SkHE while reducing current requirements. First, we demonstrate the functionalities of the SAF skyrmion logic inverter gate and other Boolean gates such as NOR, OR, AND, and NAND using the inverter gate block and show the improved performance over their ferromagnetic skyrmion gate counterparts. We analyzed the operation and energy consumption at different stages of the SAF skyrmion logic operation and found that the SAF gates can operate at lower current densities. We designed a multiplexer circuit as a test case and obtained a fast response and low Joule heating. The skyrmion motion through the gates is shown to be stable and efficient in different regions, and cascading the gates creates longer linear motion without the unwanted transverse SkHE. Overall, the results indicate the feasibility of antiferromagnetically coupled skyrmions for low-energy logic with improved performance over ferromagnetic skyrmionics.