Interplay between localization and magnetism in (Ga,Mn)As and (In,Mn)As

TL;DR

This study investigates how localization affects hole-mediated ferromagnetism in (Ga,Mn)As and (In,Mn)As, revealing that stronger p-d coupling enhances localization and influences magnetic properties near the metal-insulator transition.

Contribution

It demonstrates the impact of p-d coupling strength on localization and ferromagnetism in dilute ferromagnetic semiconductors using ion implantation and pulsed laser melting.

Findings

In1-xMnxAs shows ferromagnetic signatures at higher temperatures than Ga1-xMnxAs.

Stronger p-d coupling increases localization, reducing hole-mediated ferromagnetism.

Weakly localized holes play a key role in mediating spin interactions near the localization boundary.

Abstract

Ion implantation of Mn combined with pulsed laser melting is employed to obtain two representative compounds of dilute ferromagnetic semiconductors (DFSs): Ga1-xMnxAs and In1-xMnxAs. In contrast to films deposited by the widely used molecular beam epitaxy, neither Mn interstitials nor As antisites are present in samples prepared by the method employed here. Under these conditions the influence of localization on the hole-mediated ferromagnetism is examined in two DFSs with a differing strength of p-d coupling. On the insulating side of the transition, ferromagnetic signatures persist to higher temperatures in In1-xMnxAs compared to Ga1-xMnxAs with the same Mn concentration x. This substantiates theoretical suggestions that stronger p-d coupling results in an enhanced contribution to localization, which reduces hole-mediated ferromagnetism. Furthermore, the findings support strongly the heterogeneous model of electronic states at the localization boundary and point to the crucial role of weakly localized holes in mediating efficient spin-spin interactions even on the insulator side of the metal-insulator transition.