Double exchange mechanisms for Mn doped III-V ferromagnetic semiconductors

TL;DR

This paper introduces a microscopic model explaining ferromagnetism in Mn-doped III-V semiconductors, emphasizing hybridization and spin-selective transfer, and successfully predicts Curie temperatures aligning with experimental data.

Contribution

The paper develops a detailed microscopic model for exchange interactions in Mn-doped III-V semiconductors, highlighting hybridization effects and spin selectivity, and calculates Curie temperatures consistent with experiments.

Findings

The model explains ferromagnetism mechanisms in n-type and p-type DMS.

Calculated Curie temperatures match experimental data.

Hybridization and Hund rule effects are crucial for exchange interactions.

Abstract

A microscopic model of indirect exchange interaction between transition metal impurities in dilute magnetic semiconductors (DMS) is proposed. The hybridization of the impurity d-electrons with the heavy hole band states is largely responsible for the transfer of electrons between the impurities, whereas Hund rule for the electron occupation of the impurity d-shells makes the transfer spin selective. The model is applied to such systems as $n-$type GaN:Mn and $p-$type (Ga,Mn)As, $p-$type (Ga,Mn)P. In $n-$type DMS with Mn$^{2+/3+}$ impurities the exchange mechanisms is rather close to the kinematic exchange proposed by Zener for mixed-valence Mn ions. In $p-$type DMS ferromagnetism is governed by the kinematic mechanism involving the kinetic energy gain of heavy hole carriers caused by their hybridization with 3d electrons of Mn$^{2+}$ impurities. Using the molecular field approximation the Curie temperatures $T_C$ are calculated for several systems as functions of the impurity and hole concentrations. Comparison with the available experimental data shows a good agreement.