Role of the chiral spin configuration in field-free spin-orbit torque-induced magnetization switching by a locally injected spin current

TL;DR

This study demonstrates that a chiral spin configuration enables deterministic, field-free magnetization switching via spin-orbit torque in a localized region, advancing the development of all-electrical spintronic devices.

Contribution

It provides experimental and simulation evidence that chiral spin states can facilitate field-free SOT-induced switching in a tailored ferromagnetic system.

Findings

Chiral spin configuration enables deterministic switching without external magnetic fields.

Localized spin current induces Nel-type chiral states in the ferromagnetic layer.

Interfacial Dzyaloshinskii-Moriya interaction stabilizes or destabilizes chiral states.

Abstract

For deterministic magnetization switching by spin-orbit torque (SOT) in a perpendicular magnetic anisotropy system, an additional in-plane direction magnetic field is essential for deterministic switching by breaking the magnetization symmetry. Realizing chirality in a magnetic ordering system can be one approach for achieving asymmetry in the lateral direction for field-free magnetization switching. However, systematic analysis of the influence of the chiral spin system on deterministic switching is still scarce. In this report, the achievement of field-free SOT-induced magnetization switching by using a chiral spin configuration is investigated by experiments and micromagnetic simulations. We designed a system in which only part of the ferromagnetic layer overlaps with the heavy metal layer in the Pt/Co/MgO structure. Therefore, a spin current is exerted only on a local area of the ferromagnetic layer, which results in a N\'eel-type chiral spin configuration. The induced chiral spin configuration can be stabilized (or destabilized) depending on the sign of the interfacial Dzyaloshinskii-Moriya interaction of the system. The stabilized spin configuration plays a crucial role in the deterministic switching in zero field. We expect our findings to widen the perspective on chirality-based all-electrical SOT device fabrication.