Electronic structure and magnetism of Mn doped GaN

TL;DR

This study investigates the electronic and magnetic properties of Mn-doped GaN using first-principles calculations, revealing how Mn concentration affects impurity states, magnetic interactions, and anisotropy, with implications for spintronics.

Contribution

It provides a detailed first-principles analysis of Mn-doped GaN, highlighting differences from Mn-doped GaAs and examining the effects of electron correlation and Mn concentration on magnetic properties.

Findings

Mn impurity states form a separated impurity band at low concentration

Exchange interactions are short-ranged and anisotropic in Mn-doped GaN

Compared to Mn-doped GaAs, GaN shows different hybridization and magnetic coupling behaviors

Abstract

Mn doped semiconductors are extremely interesting systems due to their novel magnetic properties suitable for the spintronics applications. It has been shown recently by both theory and experiment that Mn doped GaN systems have a very high Curie temperature compared to that of Mn doped GaAs systems. To understand the electronic and magnetic properties, we have studied Mn doped GaN system in detail by a first principles plane wave method. We show here the effect of varying Mn concentration on the electronic and magnetic properties. For dilute Mn concentration, $d$ states of Mn form an impurity band completely separated from the valence band states of the host GaN. This is in contrast to the Mn doped GaAs system where Mn $d$ states in the gap lie very close to the valence band edge and hybridizes strongly with the delocalized valence band states. To study the effects of electron correlation, LSDA+U calculations have been performed. Calculated exchange interaction in (Mn,Ga)N is short ranged in contrary to that in (Mn,Ga)As where the strength of the ferromagnetic coupling between Mn spins is not decreased substantially for large Mn-Mn separation. Also, the exchange interactions are anisotropic in different crystallographic directions due to the presence or absence of connectivity between Mn atoms through As bonds.