A new mechanism of exchange interaction in ferromagnetic semiconductors

TL;DR

This paper introduces a novel indirect exchange interaction mechanism in ferromagnetic semiconductors, explaining ferromagnetic ordering at low carrier concentrations through hybridization and localized impurity states.

Contribution

It presents a new theoretical mechanism for exchange interaction in Mn-doped semiconductors, independent of free carrier density, expanding understanding of ferromagnetism in these materials.

Findings

Proposes a hybridization-based exchange mechanism.

Explains ferromagnetism at low carrier concentrations.

Suggests independence from free carrier density.

Abstract

We propose a new mechanism of indirect exchange interaction, which can be responsible for the ferromagnetic ordering in Mn-doped semiconductors (like GaMnAs) at low carrier concentration. The mechanism is based on the interplay of the hybridization of band states (conduction or valence) with localized impurity (donor or acceptor) states and the direct exchange interaction between localized spins and the band states. The indirect exchange coupling between two impurities occurs when the wavefunctions of the corresponding localized donor (acceptor) states overlap. This coupling is independent of the free carrier concentration and therefore may be responsible for ferromagnetic transition at low or vanishing carrier concentration.