Intrinsic hole localization mechanism in magnetic semiconductors

TL;DR

This paper investigates how clustering of Mn atoms in (Ga,Mn)As affects hole localization and magnetic interactions, revealing that Mn clustering leads to hole localization and modifies exchange coupling.

Contribution

It provides a detailed analysis of Mn atom arrangements and their impact on hole localization and magnetic exchange in (Ga,Mn)As, highlighting an intrinsic localization mechanism.

Findings

Mn clustering at nearest-neighbour Ga sites is energetically preferred.

Clustering localizes holes and reduces charge carrier concentration.

Exchange coupling increases with decreasing Mn-Mn distance.

Abstract

The interplay between clustering and exchange coupling in magnetic semiconductors for the prototype (Ga_{1-x},Mn_x)As with manganese concentrations x of 1/16 and 1/32 in the interesting experimental range is investigated. For x ~ 6 %, when all possible arrangements of two atoms within a large supercell are considered, the clustering of Mn atoms at nearest-neighbour Ga sites is energetically preferred. As shown by spin density analysis, this minimum energy configuration localizes further one hole and reduces the effective charge carrier concentration. Also the exchange coupling constant increases to a value corresponding to lower Mn concentrations with decreasing inter Mn distance.