# Current-driven domain wall dynamics in ferrimagnets: micromagnetic approach and collective coordinates model

## TL;DR

This paper presents a micromagnetic and collective coordinate model for current-driven domain wall dynamics in ferrimagnets, emphasizing the role of two coupled subsystems with distinct properties, advancing understanding beyond effective parameter models.

## Contribution

The study introduces a coupled subsystems approach for modeling ferrimagnetic domain walls, capturing detailed physical parameters and interactions beyond previous effective models.

## Key findings

- Angular momentum compensation explains linear velocity increase with current.
- Micromagnetic simulations align with the collective coordinate model.
- The approach enables predictions for experimental setups unattainable by effective models.

## Abstract

Theoretical studies dealing with current-driven domain wall dynamics in ferrimagnetic alloys and, by extension, other antiferromagnetically coupled systems as some multilayers, are here presented. The analysis has been made by means of micromagnetic simulations that consider these systems as constituted by two subsystems coupled in terms of an additional exchange interlacing them. Both subsystems differ in their respective gyromagnetic ratios and temperature dependence. Other interactions, as for example anisotropic exchange or spin-orbit torques, can be accounted for differently within each subsystem according to the physical structure. Micromagnetic simulations are also endorsed by means of a collective coordinates model which, in contrast with some previous approaches to these antiferromagnetically coupled systems, based on effective parameters, also considers them as formed by two coupled subsystems with experimentally definite parameters. Both simulations and the collective model reinforce the angular moment compensation argument as accountable for the linear increase with current of domain wall velocities in these alloys at a certain temperature or composition. Importantly, the proposed approach by means of two coupled subsystems permits to infer relevant results in the development of future experimental setups that are unattainable by means of effective models.