Kondo screening coexisting with ferromagnetic order as a possible ground state for Kondo lattice systems

TL;DR

This paper explores the coexistence of Kondo screening and ferromagnetic order in Kondo lattice systems, revealing various ground states depending on conduction electron density and coupling strength, including coexisting phases.

Contribution

It introduces a mean-field theoretical framework to analyze the coexistence of Kondo screening with ferromagnetic order in different parameter regimes.

Findings

Coexistence of Kondo screening with ferromagnetic order in certain regimes.

Identification of phase transitions driven by conduction electron density and Kondo coupling.

Magnetic field suppresses pure Kondo singlet phase, expanding ferromagnetic regions.

Abstract

We consider the competition between the Kondo screening effect and ferromagnetic long-range order (FLRO) within a mean-field theory of the Kondo lattice model for low conduction electron densities $n_{c}$. Depending on the parameter values, several types of FLRO ground states are found. When $n_{c}<0.16$, a polarized FLRO phase is dominant. For $0.16<n_{c}<0.82$, a non-polarized FLRO phase appears in the weak Kondo coupling region; while in the intermediate coupling region the ground state corresponds to the polarized and non-polarized FLRO phases, respectively, coexisting with the Kondo screening. For a strong Kondo coupling, the product of pure Kondo singlets is the ground state. Moreover, we also find that a weak magnetic field makes the pure Kondo singlet phase vanish, while the non-polarized FLRO state with the Kondo screening spans a large area in the phase diagram.