Stability of 2pi domain walls in ferromagnetic nanorings

TL;DR

This paper investigates the stability of 2pi domain walls in ferromagnetic nanorings by calculating energy barriers and analyzing the effects of ring geometry and topological differences on their stability.

Contribution

It introduces a detailed analysis of the stability and energy barriers of 2pi domain walls in ferromagnetic nanorings, considering different topological types and geometrical effects.

Findings

Stable trapped domains depend on transverse domain wall types.

Two types of 2pi walls differ by topological index and exchange energy.

Energy barriers for vortex expulsion are quantified.

Abstract

The stability of 2pi domain walls in ferromagnetic nanorings is investigated via calculation of the minimum energy path that separates a 2pi domain wall from the vortex state of a ferromagnetic nanoring. Trapped domains are stable when they exist between certain types of transverse domain walls, i.e., walls in which the edge defects on the same side of the magnetic strip have equal sign and thus repel. Here the energy barriers between these configurations and vortex magnetization states are obtained using the string method. Due to the geometry of a ring, two types of 2pi walls must be distinguished that differ by their overall topological index and exchange energy. The minimum energy path corresponds to the expulsion of a vortex. The energy barrier for annihilation of a 2pi wall is compared to the activation energy for transitions between the two ring vortex states.