Ultrafast domain wall motion in ferrimagnets induced by magnetic anisotropy gradient

TL;DR

This paper predicts and confirms through simulations that voltage-controlled magnetic anisotropy gradients can induce ultrafast domain wall motion in ferrimagnets, offering a low-power method for spintronic device control.

Contribution

It introduces a novel, theoretically predicted and simulation-verified method of driving domain walls in ferrimagnets using magnetic anisotropy gradients, advancing spintronic technology.

Findings

Ultrafast domain wall motion predicted and confirmed in ferrimagnets.

Walker breakdown depends on anisotropy and Dzyaloshinkii-Moriya interaction.

Low-power control method for future spintronic devices.

Abstract

The ultrafast magnetic dynamics in compensated ferrimagnets not only provides information similar to antiferromagnetic dynamics, but more importantly opens new opportunities for future spintronic devices [Kim et al., Nat. Mater. 16, 1187 (2017)]. One of the most essential issues for device design is searching for low-power-consuming and high-efficient methods of controlling domain wall. In this work, we propose to use the voltage-controlled magnetic anisotropy gradient as an excitation source to drive the domain wall motion in ferrimagnets. The ultrafast wall motion under the anisotropy gradient is predicted theoretically based on the collective coordinate theory, which is confirmed by the atomistic micromagnetic simulations. The antiferromagnetic spin dynamics is realized at the angular momentum compensation point, and the wall shifting has a constant speed under small gradient and can be slightly accelerated under large gradient due to the broadened wall width during the motion. For nonzero net angular momentum, the Walker breakdown occurs at a critical anisotropy gradient significantly depending on the second anisotropy and interfacial Dzyaloshinkii-Moriya interaction, which is highly appreciated for further experiments including the materials selection and device geometry design. More importantly, this work unveils a low-power-consuming method of controlling the domain wall in ferrimagnets, benefiting to future spintronic applications.