Terahertz magneto-optical response in ferromagnetic Fe-Co-Al alloys

TL;DR

This paper investigates the terahertz-range magneto-optical responses of Fe-Co-Al alloys, revealing strong frequency and composition dependence of the Hall conductivity, with potential implications for terahertz spintronics.

Contribution

It provides the first detailed theoretical analysis of the terahertz magneto-optical response in Fe-Co-Al alloys using a Kubo-based approach, highlighting composition-dependent effects.

Findings

σ_xy is strongly frequency-dependent in the terahertz range.

Adding Al to Fe can reverse the sign of σ_xy.

σ_xy varies nonmonotonically with Co concentration.

Abstract

We study the magneto-optical properties of Fe-Co-Al ordered alloys in the terahertz range of frequencies. Using the standard Kubo-based approach to compute intrinsic part of the $\sigma_{xy}(\omega)$ we find a strong dependence of $\sigma_{xy}$ on $\omega$ in the terahertz range. For example, we find that below 10~THz Co$_3$Al has nearly constant $\sigma_{xy}$ and that above 10~THz it is reduced by about 50 times. Furthermore, we find a strong dependence of $\sigma_{xy}$ on the chemical composition. For example, we find that the addition of Al to Fe changes the sign of $\sigma_{xy}$, while the addition of Co to Fe leads to a nonmonotonic dependence of $\sigma_{xy}$ on Co concentration.