Vortex stabilization in magnetic trilayer dots

TL;DR

This study numerically investigates how dipolar coupling in magnetic trilayer dots influences vortex stabilization, revealing conditions for vortex formation, triggering, and 360-degree domain walls in Co/insulator/NiFe structures.

Contribution

It provides a detailed phase diagram showing how dipolar interactions stabilize or trigger vortex states and domain walls in magnetic trilayer dots.

Findings

Dipolar coupling can stabilize vortex states in Py layers.

Co layers remain single-domain while influencing Py magnetization.

Phase diagram maps vortex and domain wall regions.

Abstract

The magnetization reversal and spin structure in circular Co/insulator/Ni80Fe20 trilayer dots has been investigated numerically. The effect of dipolar coupling between a soft ferromagnetic Permalloy (Py=Ni80Fe20) layer and a hard ferromagnetic Cobalt layer inside one stack is studied. We find either a stabilization or even a triggering of the vortex state in the Py layer due to the magnetic stray field of the Co layer, while the Co magnetization remains in a single-domain state. Furthermore, for thin Py layers a 360 deg-domain wall is observed. We construct a phase diagram, where regions of vortex stabilization, triggering, and occurrence of a 360 deg domain wall are marked.