Skyrmion nucleation via localized spin current injection in confined nanowire geometry in low chirality magnetic materials

TL;DR

This paper introduces a controlled method for nucleating single magnetic skyrmions in confined nanowires using localized spin current injection, suitable for low DMI materials and skyrmion-based devices.

Contribution

It proposes a novel, controlled skyrmion nucleation scheme in nanowires via localized spin current, involving edge domain wall pinning and annihilation processes.

Findings

Skyrmion nucleation occurs on sub-nanosecond timescale.

The method is robust to pinning site variations.

Applicable for skyrmion-based memory and logic devices.

Abstract

Magnetic skyrmions have been the focus of intense research with promising applications in memory, logic and interconnect technology. Several schemes have been recently proposed and demonstrated to nucleate skyrmions. However, they either result in an uncontrolled skyrmion bubble production or are mostly targeted towards integration with racetrack memory device. In this work, we propose a novel scheme for a controlled single skyrmion nucleation in a confined nanowire geometry with sub-100 nm width using a generalized approach of "localized spin current injection" technique in material systems exhibiting low Dzyaloshinskii-Moriya interaction (DMI). Our proposed nucleation mechanism follows a pathway involving the creation of a reversed magnetic domain containing one or more pairs of vertical Bloch lines (VBLs) that form an edge-to-edge domain wall as the VBLs get annihilated at the edge of the nanowire. However, pinning of the edge domain walls within a narrow gap using notches or anti-notches results in the creation of a magnetic bubble with defect-free domain wall that eventually relaxes into a circular skyrmion structure. Our simulations predict that the proposed mechanism allows skyrmion nucleation on sub-nanosecond timescale, shows robustness to variations like local pinning sites and is applicable for any skyrmion-based logic, memory and interconnect application.