Magnetization reversal assisted by half antivortex states in nanostructured circular cobalt disks

TL;DR

This study investigates how half antivortex states influence magnetization reversal in nanostructured circular cobalt disks with nanoholes, revealing step-like magnetic property changes relevant for spintronic memory devices.

Contribution

It demonstrates the role of half antivortices in magnetization reversal in nanostructured disks with nanoholes, supported by experiments and simulations.

Findings

Reproducible step-like changes in magnetoresistance and permeability.

Transitions between states mediated by vortices and half antivortices.

Relevance for multi-hole spintronic and magnetic memory devices.

Abstract

The half antivortex, a fundamental topological structure which determines magnetization reversal of submicron magnetic devices with domain walls, has been suggested also to play a crucial role in spin torque induced vortex core reversal in circular disks. Here we report on magnetization reversal in circular disks with nanoholes through consecutive metastable states with half antivortices. In-plane anisotropic magnetoresistance and broadband susceptibility measurements accompanied by micromagnetic simulations reveal that cobalt disks with two and three linearly arranged nanoholes directed at 45 and 135 degrees with respect to the external magnetic field show reproducible step-like changes in the anisotropic magnetoresistance and magnetic permeability due to transitions between different intermediate states mediated by vortices and half antivortices confined to the dot nanoholes and edges, respectively. Our findings are relevant for the development of multi-hole based spintronic and magnetic memory devices.