The underscreened Kondo effect: a two S=1 impurity model

TL;DR

This paper investigates the underscreened Kondo effect in a two-impurity S=1 model, revealing a continuous crossover from non-Kondo to Kondo behavior and coexistence of RKKY and Kondo effects.

Contribution

It introduces a mean-field approach to analyze the two-impurity S=1 model, showing no phase transition but a smooth crossover and asymmetric screening phenomena.

Findings

No phase transition, only a crossover from non-Kondo to Kondo behavior.

Asymmetric screening with one component strongly screened and the other nearly free.

Possible coexistence of RKKY interaction and local Kondo effect.

Abstract

The underscreened Kondo effect is studied within a model of two impurities S=1 interacting with the conduction band and via an interimpurity coupling $K\vec{S_1}.\vec{S_2}$. Using a mean-field treatment of the bosonized Hamiltonian, we show that there is no phase transition, but a continuous cross-over versus K from a non Kondo behaviour to an underscreened Kondo one. For a small antiferromagnetic coupling (K>0), a completely asymmetric situation is obtained with one s=${1/2}$ component strongly screened by the Kondo effect and the other one almost free to yield indirect magnetism, which shows finally a possible coexistence between a RKKY interaction and a local Kondo effect, as observed in Uranium compounds such as $UPt_3$.