Deterministic Helicity Locking of Bloch Skyrmions in Centrosymmetric Systems

TL;DR

This paper demonstrates a DMI-free method to deterministically control the helicity of Bloch skyrmions in centrosymmetric systems using ferromagnetic structures, enabling precise skyrmion chirality for spintronic applications.

Contribution

The study introduces a novel DMI-free approach for deterministic helicity control of skyrmions via FM/CM heterostructures and geometric design, advancing skyrmion manipulation techniques.

Findings

Geometrically constrained FM stripes stabilize specific skyrmion helicity.

Current pulses on FM notches enable deterministic nucleation of skyrmions.

Dipolar fields from heterostructures lift helicity degeneracy.

Abstract

Magnetic skyrmions in centrosymmetric materials exhibit Bloch-type spin textures with degenerate helicity states due to the absence of Dzyaloshinskii Moriya interaction (DMI), resulting in random nucleation and uncontrolled chirality. Here, we present a comprehensive micromagnetic study demonstrating a fully DMI free strategy for deterministic helicity control by interfacing ferromagnetic (FM) stripes or notch structures with centrosymmetric magnetic (CM) films. We first show that a geometrically constrained configuration comprising two FM stripes with opposite in-plane magnetizations stabilizes skyrmions with a selected helicity, either clockwise (CW) or counterclockwise (CCW). We further extend this concept to achieve deterministic nucleation of CW or CCW skyrmions using current pulses applied to an FM notch patterned on the CM film. The combined effects of the FM stripe/notch geometry and interfacial exchange coupling generate dipolar fields that lift the helicity degeneracy, enabling controlled formation of skyrmions with fixed chirality. These results establish FM/CM heterostructures as a robust, DMI-free platform for deterministic generation and guided motion of helicity-locked skyrmions, opening new pathways for advanced spintronic applications.