Remarkably robust and correlated coherence and antiferromagnetism in (Ce$_{1-x}$La$_x$)Cu$_2$Ge$_2$

H. Hodovanets; S. L. Bud'ko; W. E. Straszheim; V. Taufour; E. D. Mun; H. Kim; R. Flint; P. C. Canfield

doi:10.1103/PhysRevLett.114.236601

paper

Remarkably robust and correlated coherence and antiferromagnetism in (Ce $_{1 - x}$ La $_{x}$ )Cu $_{2}$ Ge $_{2}$

arXiv:1412.2092 · doi:10.1103/PhysRevLett.114.236601

Abstract

We present magnetic susceptibility, resistivity, specific heat, and thermoelectric power measurements on (Ce $_{1 - x}$ La $_{x}$ )Cu $_{2}$ Ge $_{2}$ single crystals (0 $\leq x \leq$ 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 $T_{co h}$ up to $\sim$ 0.9 of La, indicating a small percolation limit $\sim$ 9 $%$ of Ce that separates a coherent regime from a single-ion Kondo impurity regime. $T_{co h}$ as a function of magnetic field was found to have different behavior for $x$ < 0.9 and $x$ > 0.9. Remarkably, $(T_{co h})^{2}$ at $H$ = 0 was found to be linearly proportional to $T_{N}$ . The jump in the magnetic specific heat $δ C_{m}$ at $T_{N}$ as a function of $T_{K} / T_{N}$ for (Ce $_{1 - x}$ La $_{x}$ )Cu $_{2}$ Ge $_{2}$ follows the theoretical prediction based on the molecular field calculation for the $S$ = 1/2 resonant level model.

Remarkably robust and correlated coherence and antiferromagnetism in (Ce $_{1 - x}$ La $_{x}$ )Cu $_{2}$ Ge $_{2}$

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Remarkably robust and correlated coherence and antiferromagnetism in (Ce1−x​Lax​)Cu2​Ge2​

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Remarkably robust and correlated coherence and antiferromagnetism in (Ce $_{1 - x}$ La $_{x}$ )Cu $_{2}$ Ge $_{2}$