Weak ferromagnetism with the Kondo screening effect in the Kondo lattice systems

摘要

We carefully consider the interplay between ferromagnetism and the Kondoscreening effect in the conventional Kondo lattice systems at finitetemperatures. Within an effective mean-field theory for small conductionelectron densities, a complete phase diagram has been determined. In theferromagnetic ordered phase, there is a characteristic temperature scale toindicate the presence of the Kondo screening effect. We further find twodistinct ferromagnetic long-range ordered phases coexisting with the Kondoscreening effect: spin fully polarized and partially polarized states. Acontinuous phase transition exists to separate the partially polarizedferromagnetic ordered phase from the paramagnetic heavy Fermi liquid phase.These results may be used to explain the weak ferromagnetism observed recentlyin the Kondo lattice materials.