Metal-insulator transition by isovalent anion substitution in Ga1-xMnxAs: Implications to ferromagnetism

TL;DR

This study demonstrates that small isovalent anion substitutions in Ga1-xMnxAs induce a metal-insulator transition and significantly affect ferromagnetic properties, highlighting the role of impurity band holes and alloy disorder.

Contribution

It reveals how minimal anion substitutions cause metal-insulator transitions and alter Curie temperature, providing new insights into ferromagnetism in GaMnAs.

Findings

2.4% P substitution induces a metal-insulator transition at x=0.046.

0.4% N substitution causes crossover from metal to insulator at x=0.037.

P and N substitutions reduce Curie temperature from ~100 K to 60-65 K.

Abstract

We have investigated the effect of partial isovalent anion substitution in Ga1-xMnxAs on electrical transport and ferromagnetism. Substitution of only 2.4% of As by P induces a metal-insulator transition at a constant Mn doping of x=0.046 while the replacement of 0.4 % As with N results in the crossover from metal to insulator for x=0.037. This remarkable behavior is consistent with a scenario in which holes located within an impurity band are scattered by alloy disorder in the anion sublattice. The shorter mean free path of holes, which mediate ferromagnetism, reduces the Curie temperature TC from 113 K to 60 K (100 K to 65 K) upon the introduction of 3.1 % P (1% N) into the As sublattice.