Electronic States and Magnetism of Mn Impurities and Dimers in Narrow-Gap and Wide-Gap III-V Semiconductors

TL;DR

This study systematically investigates the electronic states and magnetic interactions of Mn impurities and dimers in narrow-gap and wide-gap III-V semiconductors, revealing hybridization-dependent magnetic coupling mechanisms.

Contribution

It introduces a detailed analysis of Mn impurity and dimer magnetic states, highlighting the role of p-d hybridization and proposing a double exchange mechanism for ferromagnetism.

Findings

AFM coupling in Mn-As complexes with strong p-d hybridization.

Weak FM coupling when hybridization is small and levels are deep.

Double-exchange-like FM coupling in Mn dimers away from half-filling.

Abstract

Electronic states and magnetic properties of single $Mn$ impurity and dimer doped in narrow-gap and wide-gap $III$-$V$ semiconductors have been studied systematically. It has been found that in the ground state for single $Mn$ impurity, $Mn$-$As(N)$ complex is antiferromagnetic (AFM) coupling when $p$-$d$ hybridization $V_{pd}$ is large and both the hole level $E_{v}$ and the impurity level $E_{d}$ are close to the midgap; or very weak ferromagnetic (FM) when $V_{pd}$ is small and both $E_{v}$ and $E_d$ are deep in the valence band. In $Mn$ dimer situation, the $Mn$ spins are AFM coupling for half-filled or full-filled $p$ orbits; on the contrast, the Mn spins are double-exchange-like FM coupling for any $p$-orbits away from half-filling. We propose the strong {\it p-d} hybridized double exchange mechanism is responsible for the FM order in diluted $III$-$V$ semiconductors.