Disentangling factors governing Dzyaloshinskii domain wall creep in Co/Ni thin films using Pt$_x$Ir$_{1-x}$ seedlayers

TL;DR

This study investigates how Pt$_x$Ir$_{1-x}$ seedlayer composition influences Dzyaloshinskii domain wall creep in Co/Ni thin films, revealing a monotonic decrease in DMI with Ir content and highlighting the role of chirality-dependent factors.

Contribution

It introduces a refined domain wall creep model incorporating anisotropic elastic energy and chirality-dependent prefactors, and demonstrates how seedlayer composition tunes DMI in magnetic thin films.

Findings

DMI decreases monotonically with increasing Ir content.

Brillouin light scattering confirms DMI trend.

Chirality-dependent attempt frequency influences domain wall dynamics.

Abstract

We characterize asymmetric growth of magnetic bubble domains in perpendicularly magnetized Co/Ni multi-layers grown on Pt$_x$Ir$_{1-x}$ seedlayers by application of perpendicular and in-plane magnetic fields. Using a refined model of domain wall creep that incorporates contributions from the anisotropic elastic energy, $\varepsilon$, and a chirality-dependent prefactor, $v_0$, we elucidate factors that govern the mobility of Dzyaloshinskii domain walls as a function of seedlayer composition. The interfacial Dzyaloshinskii-Moriya Interaction magnitude is found to decrease monotonically with $x_{Ir}$, which is independently confirmed by Brillouin light scattering (BLS). Moreover, the persistence of significant asymmetry in velocity curves across the full composition range supports previous assertions that a chirality-dependent attempt frequency akin to chiral damping could play a critical role in the observed trends. This work helps resolve fundamental questions about the factors governing Dzyaloshinskii DW creep and demonstrates varying Pt-Ir seedlayer composition as a method to tune DMI.