Influence of competing energy scales on the effective spin degeneracy in CeNi 9-xFe xGe 4

Abstract

The interplay between Kondo effect, RKKY interaction and crystal field (CF) splitting in the pseudo-ternary substitution series CeNi 9-xFe xGe 4 (0 x 1) is investigated by means of X-ray powder diffractometry and specific heat studies. Contrary to CeNi 8CuGe 4 and CeNi 8CoGe 4 no long range magnetic order occurs in CeNi 8FeGe 4 since it basically retains a four-fold degenerate Kondo lattice ground state similar to its parent system CeNi 9Ge 4. Kondo screening as well as a modest CF splitting between the two lower energy states (Γ7(1) and Γ7(2)) increase simultaneously with increasing Fe concentration resulting in a Kondo dominated ground state for the whole substitution region. A new parameter α = T R ln 4/T R ln 2 is introduced to analyze the interplay between the competing energy scales. © 2012 Elsevier B.V. All rights reserved.