Ferromagnetic Kondo-Lattice Model

TL;DR

This paper develops a comprehensive many-body approach to analyze the electronic and magnetic properties of ferromagnetic Kondo-lattice models, incorporating band structure calculations and exploring the transition between different coupling regimes.

Contribution

It introduces a novel method combining many-body theory with bandstructure calculations to study ferromagnetic Kondo-lattice systems, including multiband effects and real material applications.

Findings

Demonstrates density-dependent Curie temperature.

Shows transition from RKKY to double exchange behavior.

Applies method to EuO and EuS materials.

Abstract

We present a many-body approach to the electronic and magnetic properties of the (multiband) Kondo-lattice model with ferromagnetic interband exchange. The coupling between itinerant conduction electrons and localized magnetic moments leads, on the one hand, to a distinct temperature-dependence of the electronic quasiparticle spectrum and, on the other hand, to magnetic properties, as e.~g.the Curie temperature T_C or the magnon dispersion, which are strongly influenced by the band electron selfenergy and therewith in particular by the carrier density. We present results for the single-band Kondo-lattice model in terms of quasiparticle densities of states and quasiparticle band structures and demonstrate the density-dependence of the self-consistently derived Curie temperature. The transition from weak-coupling (RKKY) to strong-coupling (double exchange) behaviour is worked out. The multiband model is combined with a tight-binding-LMTO bandstructure calculation to describe real magnetic materials. As an example we present results for the archetypal ferromagnetic local-moment systems EuO and EuS. The proposed method avoids the double counting of relevant interactions and takes into account the correct symmetry of atomic orbitals.