The reason for the tilting of domain wall with Dzyaloshinskii-Moriya interaction from a microscopic dynamical perspective

TL;DR

This paper investigates the microscopic dynamical origins of domain wall tilting caused by Dzyaloshinskii-Moriya interaction in heavy metal/ferromagnetic heterostructures, revealing how boundary antisymmetry and initial conditions influence domain wall motion.

Contribution

It provides a micromagnetic calculation framework from a microscopic perspective to explain the tilting mechanism of domain walls due to DMI.

Findings

Boundary antisymmetry is destroyed during early CIDWM stages.

Different boundary moments undergo distinct rotation processes.

Initial conditions in Thiele equations can approximate boundary dynamics.

Abstract

The interfacial Dzyaloshinskii-Moriya interaction (DMI) of a heavy metal (HM)/ferromagnetic (FM) metal heterostructure is vital to the current-induced domain wall motion (CIDWM) at an ultrahigh velocity. However, strong DMI also tilts the moving domain wall (DW) plane, and the mechanism for this tilting is not quite clear. In this work, we have found that this tilting may be understood based on a micromagnetic calculation from a microscopic dynamical perspective. The DMI-induced antisymmetric moment structure at the two boundaries of the track needs to be paid attention. In the early stage of CIDWM induced by spin-orbit torque, this antisymmetry is destroyed. Afterwards, the moments at the two boundaries experience distinct rotation processes with different energy paths towards their final stable antisymmetric moment structure. This results in different initial velocities of the local DW regions at the two boundaries. In mathematics, this distinct DW dynamical progresses at the two boundaries can be approximately revealed by modifying the initial conditions for solving the Thiele equations.