Magnetic Impurity States and Ferromagnetic Interaction in Diluted Magnetic Semiconductors

TL;DR

This paper investigates the electronic structure of diluted magnetic semiconductors, highlighting how hybridization-induced holes around impurities facilitate ferromagnetic interactions, analyzed through an extended Haldane-Anderson model.

Contribution

It extends the Haldane-Anderson model to magnetic impurities and demonstrates the role of hole overlap in mediating ferromagnetic interactions in diluted magnetic semiconductors.

Findings

Holes are created in the valence band due to impurity-host hybridization.

Localized magnetic moments form around impurities.

Overlap of holes favors ferromagnetic interaction when impurities are close.

Abstract

The electronic structure of diluted magnetic semiconductors is studied, especially focusing on the hole character. The Haldane-Anderson model is extend to a magnetic impurity, and is analyzed in the Hartree-Fock approximation. Due to the strong hybridization of an impurity d-states with host p-states, it is shown that holes are created in the valence band, at the same time the localized magnetic moments are formed. These holes are weakly bound around the impurity site with the characteristic length of several lattice constants. For the case of the two impurities, it is found that when the separation of two impurities is of the order of the length of holes, the overlap of these holes favors the ferromagnetic interaction. The spatially extended holes play an essential role for the ferromagnetic exchange interaction.