Phase Diagram of a Model for Diluted Magnetic Semiconductors Beyond Mean-Field Approximations

TL;DR

This paper numerically investigates a lattice spin-fermion model for diluted magnetic semiconductors, revealing how Curie temperatures depend on various parameters and identifying a suppressed ferromagnetic state at large exchange interactions.

Contribution

It advances beyond mean-field approximations by numerically analyzing the model, uncovering the behavior of Curie temperatures and the emergence of a clustered state.

Findings

Curie temperature varies with Mn-spin and hole densities.

Optimal magnetic ordering occurs in an intermediate regime.

Large exchange J leads to a clustered state suppressing ferromagnetism.

Abstract

A lattice spin-fermion model for diluted magnetic semiconductors (DMS) is investigated numerically, improving on previously used mean-field (MF) approximations. Curie temperatures are obtained varying the Mn-spin x and hole n densities, and the impurity-hole exchange J in units of the hopping amplitude t. Optimal values are found in the subtle intermediate regime between itinerant and localized carriers. Our main result is the behavior of the Curie temperature at large J/t, where a "clustered" state is observed and ferromagnetism is suppressed. Formal analogies between DMS and manganites are also discussed.