Disorder Enhanced Spin Polarization in Diluted Magnetic Semiconductors

TL;DR

This theoretical study shows that in diluted magnetic semiconductors, disorder from Mn ions can enhance spin polarization despite spin-orbit coupling reducing it, affecting carrier properties and impurity band formation.

Contribution

It introduces a comprehensive model including spin-orbit coupling and disorder effects, revealing disorder's role in enhancing spin polarization in these materials.

Findings

Disorder from Mn ions enhances spin polarization.

Impurity bands form and hybridize with valence bands.

System remains metallic with large effective mass and low mobility.

Abstract

We present a theoretical study of diluted magnetic semiconductors that includes spin-orbit coupling within a realistic host band structure and treats explicitly the effects of disorder due to randomly substituted Mn ions. While spin-orbit coupling reduces the spin polarization by mixing different spin states in the valence bands, we find that disorder from Mn ions enhances the spin polarization due to formation of ferromagnetic impurity clusters and impurity bound states. The disorder leads to large effects on the hole carriers which form impurity bands as well as hybridizing with the valence band. For Mn doping 0.01 < x < 0.04, the system is metallic with a large effective mass and low mobility.