Interfacial Dzyaloshinskii-Moriya interaction in Ta\Co20Fe60B20\MgO nanowires

TL;DR

This paper investigates current-induced domain wall motion in Ta extsubscript{20}Fe extsubscript{60}B extsubscript{20} nanowires, revealing the role of Dzyaloshinskii-Moriya interaction and providing detailed modeling to extract spin-Hall angles.

Contribution

It demonstrates the presence of interfacial DMI in Ta extsubscript{20}Fe extsubscript{60}B extsubscript{20} nanowires and introduces advanced modeling to accurately determine spin-Hall angles.

Findings

Domain walls move against electron flow without magnetic field.

Positive DMI coefficient indicates right-handed domain walls.

Spin-Hall angle for Ta estimated at -0.11.

Abstract

We report current-induced domain wall motion (CIDWM) in Ta\Co20Fe60B20\MgO nanowires. Domain walls are observed to move against the electron flow when no magnetic field is applied, while a field along the nanowires strongly affects the domain wall motion direction and velocity. A symmetric effect is observed for up-down and down-up domain walls. This indicates the presence of right-handed domain walls, due to a Dzyaloshinskii-Moriya interaction (DMI) with a DMI coefficient D=+0.06 mJ/m2. The positive DMI coefficient is interpreted to be a consequence of boron diffusion into the tantalum buffer layer during annealing. In a Pt\Co68Fe22B10\MgO nanowire CIDWM along the electron flow was observed, corroborating this interpretation. The experimental results are compared to 1D-model simulations including the effects of pinning. This advanced modelling allows us to reproduce the experiment outcomes and reliably extract a spin-Hall angle {\theta}SH=-0.11 for Ta in the nanowires, showing the importance of an analysis that goes beyond the currently used model for perfect nanowires.