Jahn-Teller Distortion and Ferromagnetism in the Dilute Magnetic Semiconductors GaN:Mn

TL;DR

This study uses first-principles calculations to explore Jahn-Teller distortions and ferromagnetism in GaN:Mn, revealing significant effects in GaN but not in GaAs, with implications for magnetic properties in dilute magnetic semiconductors.

Contribution

It provides the first detailed analysis of Jahn-Teller distortions in GaN:Mn and their impact on ferromagnetism using first-principles methods.

Findings

Jahn-Teller distortion occurs in GaN:Mn but not in GaAs:Mn.

Ferromagnetism is stronger in GaN:Mn than in GaAs:Mn.

Charge compensation reduces Jahn-Teller effects and slightly decreases ferromagnetism.

Abstract

Using first-principles total-energy methods, we investigate Jahn-Teller distortions in III-V dilute magnetic semiconductors, GaAs:Mn and GaN:Mn in the cubic zinc blende structure. The results for an isolated Mn impurity on a Ga site show that there is no appreciable effect in GaAs, whereas, in GaN there is a Jahn-Teller effect in which the symmetry around the impurity changes from T$_{d}$ to D$_{2d}$ or to C$_{2v}$. The large effect in GaN occurs because of the localized d$^4$ character, which is further enhanced by the distortion. The lower symmetry should be detectable experimentally in cubic GaN with low Mn concentration, and should be affected by charge compensation (reductions of holes and conversion of Mn ions to d$^5$ with no Jahn-Teller effect). Jahn-Teller effect is greatly reduced because the symmetry at each Mn site is lowered due to the Mn-Mn interaction. The tendency toward ferromagnetism is found to be stronger in GaN:Mn than in GaAs:Mn and to be only slightly reduced by charge compensation.