Coexistence of ferromagnetism and Kondo effect in uranium compounds

TL;DR

This paper models the coexistence of ferromagnetism and Kondo effect in uranium compounds using an underscreened Kondo lattice model, showing conditions under which both phenomena can simultaneously occur.

Contribution

It introduces a lattice model with S=1 spins coupled to conduction electrons, explaining the coexistence of ferromagnetism and Kondo behavior in uranium compounds.

Findings

Kondo temperature exceeds Curie temperature, enabling coexistence.

Kondo behavior vanishes abruptly at low J_K, smoothly at different band occupations.

Model results align qualitatively with experimental observations.

Abstract

Coexistence between ferromagnetic order and Kondo behavior has been observed in some uranium compounds. The underscreened Kondo lattice model can provide a possible description of this coexistence. Here we present a model of a lattice of S=1 spins coupled to the conduction electrons through an intra-site exchange interaction $J_{K}$ and an inter-site ferromagnetic exchange $f-f$ interaction $J_{H}$. Finite temperature results show that the Kondo temperature is larger than the Curie ordering temperature, $T_{C}$, providing a possible scenario for the coexistence of Kondo effect and magnetic order. Also, the Kondo behavior disappears abruptly for low values of $J_{K}$ and smoothly when changing the band occupation. These results are in qualitative agreement with the experimental situation for the above mentioned uranium compounds.