Competition between Kondo and RKKY exchange couplings in Pu{1-x}Am{x} alloys

TL;DR

This study investigates the interplay of Kondo and RKKY interactions in Pu{1-x}Am{x} alloys using advanced computational methods, revealing that Kondo coupling strengthens with Am doping despite increased atomic volume, while RKKY weakens.

Contribution

It introduces a combined DFT and Hubbard 1 approach to quantify Kondo and RKKY couplings in Pu-Am alloys, highlighting the robustness of the Kondo effect against lattice expansion.

Findings

Kondo exchange J_K increases with Am doping.

RKKY exchange J_RKKY decreases smoothly with x.

Kondo effect remains robust despite increased atomic spacing.

Abstract

To clarify the role of the Kondo effect in screening local magnetic moments of Plutonium 5f--electrons as well as its competition to the RKKY interactions we use a combination of density functional theory with static Hartree Fock and dynamic Hubbard 1 approximations to calculate the strength of both the Kondo exchange, J_K, and of the RKKY exchange, J_RKKY, couplings for Pu{1-x}Am{x} system as a function of x. We find that J_K increases despite the atomic volume gets larger with the Am doping due to unexpected enhancement of hybridization between f and conduction electrons in the vicinity of the Fermi level. At the same time, the RKKY exchange is shown to reduce smoothly with increasing x. Our results imply that the Kondo effect should be robust against the increase in interatomic spacing of this alloy.