Controlling Curie temperature in (Ga,Ms)As through location of the Fermi level within the impurity band

TL;DR

This paper investigates how the position of the Fermi level within the impurity band influences the Curie temperature in (Ga,Mn)As, challenging the traditional valence band hole model and suggesting new pathways for enhancing ferromagnetic properties.

Contribution

It provides experimental evidence that the Fermi level location within the impurity band, not the valence band, controls the Curie temperature in (Ga,Mn)As.

Findings

Fermi level position within impurity band affects TC

Hole localization correlates with Curie temperature

Results challenge the valence band hole model

Abstract

The ferromagnetic semiconductor (Ga,Mn)As has emerged as the most studied material for prototype applications in semiconductor spintronics. Because ferromagnetism in (Ga,Mn)As is hole-mediated, the nature of the hole states has direct and crucial bearing on its Curie temperature TC. It is vigorously debated, however, whether holes in (Ga,Mn)As reside in the valence band or in an impurity band. In this paper we combine results of channeling experiments, which measure the concentrations both of Mn ions and of holes relevant to the ferromagnetic order, with magnetization, transport, and magneto-optical data to address this issue. Taken together, these measurements provide strong evidence that it is the location of the Fermi level within the impurity band that determines TC through determining the degree of hole localization. This finding differs drastically from the often accepted view that TC is controlled by valence band holes, thus opening new avenues for achieving higher values of TC.