Self focusing Hybrid Skyrmions in spatially varying canted ferromagnetic systems

TL;DR

This paper introduces self-focusing hybrid skyrmions in ferromagnetic systems with spatially varying Dzyaloshinskii-Moriya interactions, enabling controlled, boundary-free skyrmion motion for potential memory applications.

Contribution

It demonstrates how spatially varying DMI can induce self-focusing of hybrid skyrmions, allowing for boundary-free, controllable skyrmion trajectories in racetrack memory devices.

Findings

Hybrid skyrmions travel parallel to racetracks with zero Magnus force.

Spatial DMI variation causes skyrmions to self-focus onto tracks.

Voltage-controlled magnetic anisotropy enables trajectory control.

Abstract

Magnetic skyrmions are quasiparticle configurations in a magnetic film that can act as information carrying bits for ultrasmall, all-electronic nonvolatile memory. The skyrmions can be nucleated and driven by spin-orbit torque from a current driven in a heavy metal underlayer. Along its gyrotropic path, a Magnus force can cause a skyrmion to be annihilated at the boundaries. By combining interfacial and bulk Dzyaloshinskii-Moriya interactions (DMIs), for instance by using a B20 material on top of a heavy metal layer with high spin-orbit coupling, it is possible to engineer a hybrid skyrmion that will travel parallel to the racetrack with zero Magnus force. We show that by using a spatially varying interfacial DMI, a hybrid skyrmion will automatically self-focus onto such a track as its domain angle evolves along the path. Furthermore, using a gate driven voltage controlled magnetic anisotropy, we can control the trajectory of the hybrid skyrmion and its eventual convergence path and lane selection in a racetrack geometry.