Study of the velocity plateau of Dzyaloshinskii domain walls

TL;DR

This paper investigates the behavior of Dzyaloshinskii domain walls in multilayer magnetic films, revealing a velocity plateau at high fields and analyzing how material properties influence this phenomenon through experiments and simulations.

Contribution

It introduces a physical model explaining the microscopic origin of the velocity plateau in Dzyaloshinskii domain walls, supported by experimental and simulation data.

Findings

Velocity plateau observed at high fields in domain wall motion.

Maximum speed and plateau extent depend on magnetization, DMI strength, and anisotropy.

Micromagnetic simulations successfully reproduce experimental features.

Abstract

We study field-driven domain wall (DW) velocities in asymmetric multilayer stacks with perpendicular magnetic anisotropy and Dzyaloshinskii-Moriya interaction (DMI), both experimentally and by micromagnetic simulations. Using magneto-optical Kerr microscopy under intense and nanoseconds-long fields, we show that DWs in these films propagate at velocities up to hundreds of m/s and that, instead of the expected decrease of velocity after the Walker field, a long plateau with constant velocity is observed, before breakdown. Both the maximum speed and the field extent of the velocity plateau strongly depend on the values of the spontaneous magnetization and the DMI strength, as well as on the magnetic anisotropy. Micromagnetic simulations reproduce these features in sufficiently wide strips, even for perfect samples. A physical model explaining the microscopic origin of the velocity plateau is proposed.