Coexistence of ferromagnetism and Kondo effect in uranium compounds

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.