Electronic structure and exchange constants in magnetic semiconductors digital alloys: chemical and band-gap effects

TL;DR

This study uses first-principles simulations to analyze how band-gap size and host material influence magnetic exchange interactions in Mn-based digital alloys, revealing that larger band-gaps enhance ferromagnetic coupling.

Contribution

It provides a comparative analysis of electronic and magnetic properties of Mn/Ge and Mn/GaAs digital alloys, highlighting the effects of chemical composition and band-gap on exchange constants.

Findings

Larger band-gap increases ferromagnetic coupling in Mn/Ge.

Mn/GaAs shows smaller nearest-neighbor ferromagnetic exchange than Mn/Ge.

Both systems exhibit similar overall magnetic behavior despite differences.

Abstract

First-principles simulations have been performed for [001]-ordered Mn/Ge and Mn/GaAs "digital alloys", focusing on the effects of i) a larger band-gap and ii) a different semiconducting host on the electronic structure of the magnetic semiconductors of interest. Our results for the exchange constants in Mn/Ge, evaluated using a frozen-magnon scheme, show that a larger band-gap tends to give a stronger nearest-neighbor ferromagnetic coupling and an overall enhanced in-plane ferromagnetic coupling even for longer-ranged coupling constants. As for the chemical effects on the exchange constants, we show that Mn/GaAs shows a smaller nearest-neighbor ferromagnetic coupling than Mn/Ge, but exchange constants for higher Mn-Mn distance show an overall increased ferromagnetic behavior in Mn/GaAs. As a result, from the magnetic-coupling point of view, the two systems behave on average rather similarly.