Change of the Kondo regime inCePd2Al3induced by chemical substitution: Verification of the Doniach diagram

Abstract

We report on measurements of specific heat and resistivity for the series of compounds (La 1Ϫx Ce x )Pd 2 Al 3 , for 0рxр1. The chemical substitution with La promotes an increase of the unit cell volume, which is responsible for the changes observed for the ground state of the system. The resistivity results show two distinct behaviors: the Kondo single impurity for low Ce concentration and the Kondo lattice regime for the other end. From the magnetic specific heat results we estimated the Kondo temperature (T K ). Our results show that T K increases monotonously with Ce concentration but with a strong variation of the Néel temperature. We also estimated the s-f exchange parameter and density of states for the whole series of compounds. A Doniach type diagram is presented including the literature data obtained from pressure experiments.

Influence of Anomalous Changes in the Crystal Structure on the Transport Properties of YbNi1−xCuxAl Series of Alloys

“…The ratio of the high- and low-temperature slopes for x = 0.5 compound is around 5.1. This fact is consistent with a doublet ground state and a doublet excited state according to the Cornut–Coqblin model developed for Ce compounds [ 16 , 17 , 23 , 24 ]. However, for x = 0.8, the ratio is around 1.2, which indicates that this model could partially fail for the case of Yb-based alloys or additional effects must be taken into account [ 17 , 23 ].…”

“…This fact is consistent with a doublet ground state and a doublet excited state according to the Cornut–Coqblin model developed for Ce compounds [ 16 , 17 , 23 , 24 ]. However, for x = 0.8, the ratio is around 1.2, which indicates that this model could partially fail for the case of Yb-based alloys or additional effects must be taken into account [ 17 , 23 ]. The presence of crystalline field effects is clearly visible with a hump around 60 K (regions where the two slopes separate each other), which further indicates the splitting of the first excited state around 90 K [ 24 ].…”

“…To extract the magnetic contribution ρ mag vs. temperature in the Yb-based series YbNi 1−x Cu x Al, the resistivity of the nonmagnetic Y-based counterparts was subtracted, as presented in Figure 5 . The resulting curves display two regions with −lnT dependence, characteristic of a Kondo interaction in the presence of crystalline field effects [ 16 , 17 , 23 , 24 ]. In hexagonal symmetry, the eightfold degenerate state of the Yb 3+ ion with J = 7/2 is expected to split into four doublets [ 25 ].…”

Breakdown of the coherence effects and Fermi liquid behavior in YbAl3nanoparticles

“…Irrespective of this qualitative interpretation, what is clear is that by reducing the size, a ρ(T) minimum appears with the low temperature upturn. As a matter of fact, this situation resembles the cases of bulk alloys under chemical substitution, in which by adding non-magnetic rareearth atoms (Y and La for Ce-based and La or Lu for Yb-based compounds) a transition from Kondo lattice to single impurity regime is observed (see for instance [12,17]. In bulk YbAl 3 the coherence scattering is maintained throughout the alloy as a result of Kondo lattice behavior.…”

Kondo effect in the quasiskutteruditeYb3Os4Ge13

“…The logarithmic divergence at low temperatures indicates a possible Kondo contribution [33] below 40 K.…”