Remarkably robust and correlated coherence and antiferromagnetism in (Ce_1-xLa_x)Cu₂Ge₂

2014/12/31 by H. Hodovanets, S. L. Bud'ko, W. E. Straszheim +5 · 1 citation
Physics and Astronomy · #cond-mat.str-el

paper · pdf · doi:10.1103/physrevlett.114.236601

published as Phys. Rev. Lett. 114, 236601 (2015)

arxiv created 2015/08/31 · arxiv updated 2015/09/01

Abstract

We present magnetic susceptibility, resistivity, specific heat, and thermoelectric power measurements on (Ce_1-xLa_x)Cu₂Ge₂ single crystals (0 ≤ x≤ 1). With La substitution, the antiferromagnetic temperature T_N is suppressed in an almost linear fashion and moves below 0.36 K, the base temperature of our measurements for x> 0.8. Surprisingly, in addition to robust antiferromagnetism, the system also shows low temperature coherent scattering below T_coh up to ∼ 0.9 of La, indicating a small percolation limit ∼ 9% of Ce that separates a coherent regime from a single-ion Kondo impurity regime. T_coh as a function of magnetic field was found to have different behavior for x< 0.9 and x> 0.9. Remarkably, (T_coh)² at H = 0 was found to be linearly proportional to T_N. The jump in the magnetic specific heat δC_m at T_N as a function of T_K/T_N for (Ce_1-xLa_x)Cu₂Ge₂ follows the theoretical prediction based on the molecular field calculation for the S = 1/2 resonant level model.

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