The Kondo Lattice Models and Magnetism for Cerium and Uranium Systems

Abstract

The interplay between the Kondo effect and magnetism is important in anomalous rare-earth and actinide systems and a brief review of the different Kondo lattice models is presented here. The first studied case is the classical Kondo lattice model with S = 1/2 spins for the 4f localized electrons, which describes the strong competition between the Kondo effect and magnetic ordering leading to small ordering temperatures less than roughly 10 K. The second reviewed case describes the underscreened Kondo lattice model with S = 1 spins for the 5f localized electrons, which can account for the coexistence of both the Kondo effect and the ferromagnetic order and, therefore, the large Curie temperatures observed in actinide compounds like UTe and NpNiSi2; the question of the delocalization of the 5f electrons is also discussed here. The last case describes the competition between the "spin glass" behaviour, the Kondo effect and the magnetic ordering in disordered cerium alloys like CeNixCu1−x or CeRhxPd1−x and several models used for the spin glass state are reviewed, as well as the occurrence of magnetic glass clusters.

Effective mass enhancement and spin-glass behaviour in CeCu4MnyAl1−ycompounds

“…This change of the θ p sign supports, therefore, the conclusions derived from the behaviour of the electronic specific heat coefficient and the region of y ≈ 0.3 seems to be a threshold below which the HF state coexists with or dominates over the SG state. The problem of the SG-HF coexistence has already been studied theoretically and only a few experimental observations have been reported [3,6,7,28,[32][33][34][35]. Even if the SG state exists down to y = 0 its nature changes probably around y ≈ 0.3 from SG resulting from the frustration of the magnetic interactions for Mn-rich samples to SG caused by the NMAD behaviour in the Al-rich compounds.…”

Substitutional effects of In by Cu in CeIn2

“…It has also been shown that in disordered Ce alloys, the competition between ferromagnetism, SG and Kondo effect is crucial in defining the ground state and the magnetic behavior in these systems [12,13]. However, further experimental work would be necessary to evaluate the balance between these interactions.…”

Specific Heat Behavior in the Kondo Lattice Model With Hybridization Interaction Under Low Temperature Regimes

“…Many approximation techniques, however, were developed in the 80s based on treating 1/N as a small parameter'. These methods were used to calculate the one electrons density of states and the dynamics susceptibility [Coqblin, 2010]. What they clearly showed was the buildup of a narrow many body resonance in the density of states at the Fermi level in the Kondo regime known as the Kondo resonance.…”