Band model for the understanding of ferromagnetism in semiconductors and insulators

TL;DR

This paper introduces a hybridized Kondo-lattice model to better understand ferromagnetism in semiconductors and insulators, accounting for localized moments and conduction electrons, and explores their temperature-dependent magnetic properties.

Contribution

It develops a novel hybridized Kondo-lattice model incorporating localized and conduction electrons to analyze ferromagnetic behavior in semiconductors and insulators.

Findings

Temperature-dependent phase diagrams are provided for different parameters.

Quasiparticle densities of states are analyzed.

The influence of localized electron energy levels is discussed.

Abstract

To investigate ferromagnetic semiconductors and insulators, such as the famous EuO, EuS, or CrBr$_3$, we propose a hybridized Kondo-lattice model, where, in addition to the conduction electrons, localized moments (e.g., the $4f$-electrons) are modeled as a strongly correlated band system. The quasi-empty conduction band is weakly filled due to the hybridization term. This activates the intraatomic exchange coupling between conduction and localized electrons. Temperature-dependent phase diagrams and quasiparticle densities of states are presented for various coupling and hybridization strengths. Moreover, the influence of the one-particle energy of the localized electrons $E_f$ is discussed. A comparison with mean field calculations is given at the end of this work.