The development of skyrmion-based racetrack memory is hindered by the dual challenges of maintaining skyrmion-chain synchronization and preventing end clogging. Through micromagnetic simulations, we demonstrate that synthetic antiferromagnetic (SyAF) nanotracks overcome these issues via two key mechanisms. First, robust synchronization is achieved with an optimal intralayer spacing of 1.1 lD, larger than the 0.9 lD required in single-layer systems due to enhanced repulsive interactions in SyAF structures. Second, by engineering a triangular defect at the terminus of a single ferromagnetic layer, end clogging is suppressed while dramatically reducing the critical current density (Jcr) for clogging-free operation. Jcr exhibits a distinct dependence on the defect’s apex angle (θ), increasing gradually for θ 90° and sharply for θ 90°. Optimized defects with a universal height of 32 nm enable reliable operation across a wide angular range (20°–90°) at substantially reduced current densities, representing a nearly two-order-of-magnitude improvement over conventional designs. This work provides fundamental insights and practical design guidelines for high-density, efficient skyrmion memory devices.
Zhang et al. (Mon,) studied this question.