Suppression of the repulsion phenomenon of magnetic skyrmions at the end of synthetic antiferromagnetic racetracks

Abstract

The synthetic antiferromagnetic (SAF) racetracks can perfectly suppress the skyrmion Hall effect, but the congestion phenomenon of the skyrmions at the end of the racetracks will seriously hinder the development of the skyrmion-based magnetic storage technology. In this paper, we have designed and investigated three racetrack structures of double-layer triangular notch, single-layer triangular notch (SLTN) and square hole-triangular notch (SHTN) in SAF racetracks by micromagnetic simulations. The critical current density that annihilates skyrmions in a racetrack with triangular notches is closely related to the angle of the triangular notches and decreases with the decrease of the angles. If a skyrmion in the top ferromagnetic (FM) layer of SLTN structure is annihilated, its counterpart in the bottom FM layer will also be annihilated due to the interlayer antiferromagnetic exchange coupling. Compared with the critical current density of 3.0 × 1012 A m−2 in a normal racetrack, the critical current density of SHTN structure can be dropped to 6.0 × 1010 A m−2. The results reveal that all the three structures can significantly reduce the critical current density, which can effectively solve the skyrmion congestion at the end of the racetracks.