Exchange interactions and Curie temperature in (GaMn)As

TL;DR

This study investigates how Mn concentration affects magnetic interactions and Curie temperature in (GaMn)As, revealing a nonmonotonous dependence and emphasizing the role of hole states in mediating exchange interactions.

Contribution

The paper provides detailed calculations of exchange interactions and Curie temperature dependence on Mn and hole concentrations in (GaMn)As using supercell and frozen-magnon methods.

Findings

Curie temperature varies nonmonotonously with Mn concentration.

Decreasing hole concentration rapidly lowers the Curie temperature.

Valence band holes are more effective in mediating exchange than conduction band electrons.

Abstract

We use supercell and frozen-magnon approaches to study the dependence of the magnetic interactions in (Ga,Mn)As on the Mn concentration. We report the parameters of the exchange interaction between Mn spins and the estimates of the Curie temperature within the mean-field and random-phase approximations. In agreement with experiment we obtain a nonmonotonous dependence of the Curie temperature on the Mn concentration. We estimate the dependence of the Curie temperature on the concentration of the carries in the system and show that the decrease of the number of holes in the valence band leads to fast decrease of the Curie temperature. We show that the hole states of the valence band are more efficient in mediating the exchange interaction between Mn spins than the electron states of the conduction band.