Magnetic skyrmions without the skyrmion Hall effect in a magnetic nanotrack with perpendicular anisotropy

Abstract

Magnetic skyrmions have potential applications in novel information devices with excellent energy efficiency. However, the skyrmion Hall effect (SkHE) could cause skyrmions moving in a nanotrack to get annihilated at the track edge. In this work, we discovered that the SkHE is depressed by modifying the magnetic structure at the edge of a track, and thus the skyrmion can move in almost a straight line at a high speed. Unlike the inner part of a track with perpendicular magnetic anisotropy, the edge layer exhibits in-plane magnetic anisotropy, and the orientation of edge moments is opposite that at the perimeter of skyrmions nearby. As a result, an enhanced repulsive force acts on the skyrmion to oppose the Magnus force that causes the SkHE. Additionally, the Dzyaloshinskii-Moriya interaction (DMI) constant of the edge layer also matters. When there is no DMI at the edge layer, the transverse displacement of the skyrmion can be depressed effectively when the width of the edge layer is sufficiently large. However, when the inner part and the edge share the same DMI constant, non-monotonically varied transverse displacement occurs because of the Néel-wall-like structure at the edge layer.

Efficient in-line skyrmion injection method for synthetic antiferromagnetic systems

“…However, the energy change is offset by the increase in exchange energy, resulting in a net linear increase of energy in the system. The change in magnetostatic energy is consistent with the DW areal energy density given by equation (1).…”

“…In figure 4, we demonstrate the writing of two skyrmions followed by a shift operation and finally the deletion of the first skyrmion. While the nucleation and manipulation of only two skyrmions was demonstrated, the proposed device has a storage capacity that is similar to the well-studied skyrmion racetrack memory devices [1,2,5,7,12,35]. Skyrmion shifting is achieved by the application of a current density along the axis of the nanowire.…”

“…Magnetic skyrmions are bubble-like magnetization configurations that exist in the nanometer length scale. Due to their many attractive attributes as a candidate for a universal memory, they have been at the center of much scientific endeavors [1][2][3][4][5][6][7]. However, a few persistent challenges hinder the realization of the skyrmionic memory.…”

“…First of which is the presence of a skyrmion Hall effect which leads to a transverse motion of the skyrmion under an electric current. This behavior often leads to skyrmion annihilation at the nanowire edges and imposes a speed limit for skyrmions [1,5,[8][9][10][11][12]. Secondly, as skyrmions are magnetically charged, they experience significant repulsion with each other [6].…”

Spin current pumped by confined breathing skyrmion

“…The DMI is one of the most important parameters to form skyrmions in the magnetic systems and indispensable for a nanoscale skyrmion [27]. In addition, the modulation of DMI is also one of the methods [28][29][30] to prevent the skyrmion Hall effect. We usually define the helicity of skyrmion by the phase χ [20] appearing in φ(ϕ) = N sk ϕ + χ, where the N sk is defined as the skyrmion number.…”