Domain wall profiles in Co/Ir$_n$/Pt(111) ultrathin films: influence of the Dzyaloshinskii-Moriya interaction

TL;DR

This study investigates how Ir buffer layers influence domain wall structures and Dzyaloshinskii-Moriya interactions in Co/Pt(111) ultrathin films through first-principles calculations and spin dynamics simulations.

Contribution

It provides detailed analysis of the impact of Ir buffer layers on magnetic interactions and domain wall chirality in Co/Ir$_n$/Pt(111) films, including a micromagnetic model extension.

Findings

Domain walls are of Neel type with chirality affected by Ir layers.

Ir buffer layers induce a twisting of spins in the domain walls.

The study extends micromagnetic models with additional energy terms.

Abstract

We perform a study of domain walls in Co/Ir$_n$/Pt(111) (n = 0,1,...,6) films by a combined approach of first-principles calculations and spin dynamics simulations. We determine the tensorial exchange interactions and the magnetic anisotropies for the Co overlayer in both FCC and HCP geometries, depending on the number of Ir buffer layers. We find strong ferromagnetic nearest-neighbor isotropic exchange interactions between the Co atoms and an out-of-plane magnetic anisotropy for the films in FCC geometry. Our simulations show that the magnetic domain walls are of N\'eel type, and their rotational sense (chirality) is changed upon the insertion of an Ir buffer layer as compared to the pristine Co/Pt(111) system. Our spin dynamics simulations indicate a twisting of the spins with respect to the planar domain wall profile on the triangular lattice. We discuss this domain wall twisting using symmetry arguments and in terms of an appropriate micromagnetic continuum model considering extra energy terms compared to the available literature.