Very large domain wall velocities in Pt/Co/Gd trilayers with Dzyaloshinskii-Moriya interaction

TL;DR

This study demonstrates that asymmetric Pt/Co/Gd trilayers exhibit very high domain wall velocities driven by Dzyaloshinskii-Moriya interaction, with speeds up to 600 m/s, influenced by interfacial magnetic coupling.

Contribution

It provides experimental evidence linking large domain wall velocities to DMI strength and interfacial magnetic coupling in Pt/Co/Gd trilayers, expanding understanding of chiral magnetic dynamics.

Findings

Asymmetric samples show higher DW velocities than symmetric ones.

Maximum DW speed scales with DMI strength over magnetization.

Gd/Co interface coupling reduces magnetization, enhancing DW speed.

Abstract

We carried out measurements of domain wall (DW) velocities driven by magnetic field pulses in symmetric Pt/Co/Pt and asymmetric Pt/Co/AlOx, Pt/Co/GdOx and Pt/Co/Gd trilayers with ultrathin Co layers and perpendicular magnetic anisotropy. In agreement with theoretical models, the maximum observed velocity is much larger in the asymmetric samples, where the interfacial Dzyaloshinskii-Moriya interaction (DMI) stabilises chiral N\'eel walls, than in the symmetric stack. In addition, in Pt/Co/Gd very large DW speeds (up to 600 m/s) are obtained, 2.5 times larger than in samples with oxidised Gd. Magnetic measurements reveal that this may be explained by the anti-parallel coupling between the magnetic moments of Gd and Co at the Gd/Co interface, leading to a decrease of the total magnetisation. In quantitative agreement with analytical models, in all samples the maximum observed DW speed scales as D=Ms, where D is the strength of the DMI and Ms the spontaneous magnetisation.