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H. Michor, K. Kreiner, N. Tsujii, K. Yoshimura, K. Kosuge, G. Hilscher:
"Crystalline electric field and Kondo energy scales in YbCu_5-xAg_x";
Physica, B 319 (2002), S. 277 - 281.

Abstract

The specific heat of LuCu5-xAgx reference samples was measured to reanalyse the heavy-fermion behaviour of the isostructural AuBe5-type cubic system YbCu5-xAgx with x=0¯1 which is a series of dense Kondo compounds whose characteristic temperature T0 decreases as x decreases. For YbCu5-xAgx, the small gamma, Greek-value increases from 210 mJ/molK2 for x=1.0 to 550 mJ/molK2 for x=0.0. The analysis of the magnetic susceptibility and of the magnetic contribution to the specific heat in terms of Coqblin¯Schrieffer (CS) model reveals a significant reduction of the effective ground state degeneracy: While YbCu4Ag is well described by the CS model with View Image and T0=150 K, one has to consider a crystalline electric field splitting of the Yb3+ ground state multiplet with an energy scale of the order of 80 K and a Kondo contribution corresponding to the CS model with View Image and T0~30 K in the case of YbCu5, i.e. there is a cross-over of the characteristic energy scales of the Kondo interaction and of the CEF splitting within the series Yb(Cu,Ag)5.

Author Keywords: Kondo effect; Crystalline electric field; Specific heat

PACS classification codes: 75.20.Hr; 75.10.Dg; 65.40.Ba
Article Outline

1. Introduction
2. Experimental details
3. Results of the specific heat measurements on LuCu5-xAgx
4. Discussion of the solid solution YbCu5-xAgx
5. Conclusions
References


Enlarge Image (8K)
Fig. 1. The specific heat, Cp(T), of LuCu5-xAgx with x=1.0, 0.5, 0.25 and 0.0 as labelled; for clarity, constant values of 10, 20 and 30 J/molK have been added to the data for x=0.5, 0.25 and 0.0, respectively.

Enlarge Image (7K)
Fig. 2. The magnetic susceptibility, small chi, Greek(T) of YbCu5-xAgx taken from [8 and 9]. The dashed line corresponds to the J=7/2 CS result with T0=160 K; the full line shows the J=3/2 CS result with T0=40 K.

Enlarge Image (18K)
Fig. 3. The magnetic specific heat, capital Delta, GreekCp(T)/T versus T, of YbCu5-xAgx shown on linear scale (a) and logarithmic scale (b). The full lines correspond to the CS model with J=7/2 and T0=160 K (line 1), J=5/2 with T0=80 K (line 2) and J=3/2 with T0=26 K (line 3).

Enlarge Image (8K)
Fig. 4. The magnetic specific heat, capital Delta, GreekCp(T), of YbCu5 (for details see text).
References

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Physica B: Condensed Matter
Volume 319, Issues 1-4, July 2002, Pages 277-281

http://dx.doi.org/10.1016/S0921-4526(02)01129-8