High Curie temperatures in (Ga,Mn)N from Mn clustering

TL;DR

This study uses density-functional calculations to show that microscopic Mn cluster arrangements in (Ga,Mn)N significantly influence the Curie temperature, explaining experimental variations and identifying configurations that yield high Tc above room temperature.

Contribution

It reveals how specific Mn cluster distributions affect Tc in (Ga,Mn)N, highlighting the role of Mn dimers in achieving high Curie temperatures.

Findings

Mn cluster distribution crucially affects Tc.

Mn_2 dimers enhance Tc above 500 K.

Certain Mn arrangements lead to near-zero Tc.

Abstract

The effect of microscopic Mn cluster distribution on the Curie temperature (Tc) is studied using density-functional calculations. We find that the calculated Tc depends crucially on the microscopic cluster distribution, which can explain the abnormally large variations in experimental Tc values from a few K to well above room temperature. The partially dimerized Mn_2-Mn_1 distribution is found to give the highest Tc > 500 K, and in general, the presence of the Mn_2 dimer has a tendency to enhance Tc. The lowest Tc values close to zero are obtained for the Mn_4-Mn_1 and Mn_4-Mn_3 distributions.