Fast domain wall motion induced by antiferromagnetic spin dynamics at the angular momentum compensation temperature of ferrimagnets

TL;DR

This paper demonstrates that at the angular momentum compensation temperature, ferrimagnets exhibit ultrafast antiferromagnetic domain wall motion driven by magnetic fields, revealing new physics and potential for high-speed spintronic devices.

Contribution

It provides experimental evidence of fast field-driven antiferromagnetic domain wall motion at the angular momentum compensation point in ferrimagnets, a phenomenon previously unexplored due to antiferromagnets' magnetic field immunity.

Findings

Field-driven DW mobility up to 20 km/sT at TA

Enhanced antiferromagnetic spin dynamics at TA

Validation through atomistic spin model simulations

Abstract

Antiferromagnetic spintronics is an emerging research field which aims to utilize antiferromagnets as core elements in spintronic devices. A central motivation toward this direction is that antiferromagnetic spin dynamics is expected to be much faster than ferromagnetic counterpart because antiferromagnets have higher resonance frequencies than ferromagnets. Recent theories indeed predicted faster dynamics of antiferromagnetic domain walls (DWs) than ferromagnetic DWs. However, experimental investigations of antiferromagnetic spin dynamics have remained unexplored mainly because of the immunity of antiferromagnets to magnetic fields. Furthermore, this immunity makes field-driven antiferromagnetic DW motion impossible despite rich physics of field-driven DW dynamics as proven in ferromagnetic DW studies. Here we show that fast field-driven antiferromagnetic spin dynamics is realized in ferrimagnets at the angular momentum compensation point TA. Using rare-earth 3d-transition metal ferrimagnetic compounds where net magnetic moment is nonzero at TA, the field-driven DW mobility remarkably enhances up to 20 km/sT. The collective coordinate approach generalized for ferrimagnets and atomistic spin model simulations show that this remarkable enhancement is a consequence of antiferromagnetic spin dynamics at TA. Our finding allows us to investigate the physics of antiferromagnetic spin dynamics and highlights the importance of tuning of the angular momentum compensation point of ferrimagnets, which could be a key towards ferrimagnetic spintronics.