Competition between terahertz magnetoelectric and N\'eel spin-orbit torque driven spin dynamics in metallic antiferromagnets

TL;DR

This paper demonstrates that THz electric fields can induce significant spin dynamics in metallic antiferromagnets like Mn2Au through magnetoelectric effects, competing with Néel spin-orbit torques, which is crucial for understanding ultrafast spin behavior.

Contribution

The study provides a theoretical analysis showing that THz magnetoelectric effects in metallic antiferromagnets are non-negligible and must be considered alongside Néeel spin-orbit torques.

Findings

THz electric fields induce measurable spin dynamics in Mn2Au.

Magnetoelectric torque is proportional to the time derivative of the induced polarization.

Competition between magnetoelectric and Néeel spin-orbit torques explains experimental results.

Abstract

Although magnetoelectric effects in metals are usually neglected, assuming that applied electric fields are screened by free charge carriers, the skin depth, defining the penetration depth of the fields, is non-zero and for THz electric fields typically reaches 400 nm. Hence, if the thickness of an antiferromagnetic film is of the order of tens of nm, electric field induced effects cannot be neglected. Here, we theoretically study the THz electric field induced spin dynamics in the metallic antiferromagnet $\mathrm{Mn}_{2}\mathrm{Au}$, whose spin arrangements allow it to exhibit a linear magnetoelectric effect. We show that the THz magnetoelectric torque in metallic antiferromagnets is proportional to the time derivative of the polarization induced by the THz electric field. Our simulations reveal that the magnetoelectric driven spin dynamics is indeed not negligible, and for a fair explanation of previously published experimental results in $\mathrm{Mn}_{2}\mathrm{Au}$ competition between THz magnetoelectric and N\'eel spin-orbit torques must be taken into account. Thus, it is shown that even in metallic antiferromagnets the THz magnetoelectric effect on spins can be strong and thus cannot be neglected.