Ground state and constrained domain walls in Gd/Fe multilayers

TL;DR

This paper models the magnetic ground states and domain wall behaviors in Gd/Fe multilayers, revealing how layer thickness and magnetic moment ratios influence the formation of twisted states and domain wall overlap.

Contribution

It introduces a micromagnetic model to analyze how layer thickness and magnetic moments affect the ground state and domain walls in Gd/Fe multilayers, highlighting the role of interface domain wall overlap.

Findings

Twisted states appear at low fields for certain M(Fe):M(Gd) ratios.

Thicker layers favor twisted states over aligned states.

Ultrathin layers prevent wide domain wall formation, excluding twisted states.

Abstract

The magnetic ground state of antiferromagnetically coupled Gd/Fe multilayers and the evolution of in-plane domain walls is modelled with micromagnetics. The twisted state is characterised by a rapid decrease of the interface angle with increasing magnetic field. We found that for certain ratios M(Fe):M(Gd), the twisted state is already present at low fields. However, the magnetic ground state is not only determined by the ratio M(Fe):M(Gd) but also by the thicknesses of the layers, that is the total moments of the layer. The dependence of the magnetic ground state is explained by the amount of overlap of the domain walls at the interface. Thicker layers suppress the Fe aligned and the Gd aligned state in favour of the twisted state. Whereas ultrathin layers exclude the twisted state, since wider domain walls can not form in these ultrathin layers.