Remarkably Robust and Correlated Coherence and Antiferromagnetism in (Ce1-xLax)Cu2Ge2

Abstract

<p>We present magnetic susceptibility, resistivity, specific heat, and thermoelectric power measurements on (Ce1−xLax)Cu2Ge2 single crystals (0≤x≤1). With La substitution, the antiferromagnetic temperature TN 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 Tcoh up to ∼0.9 of La, indicating a small percolation limit ∼9% of Ce. Tcoh as a function of magnetic field was found to have different behavior for x<0.9 and x>0.9. Remarkably, (Tcoh)2 at H=0 was found to be linearly proportional to TN. The jump in the magnetic specific heat δCm at TN as a function of TK/TN for (Ce1−xLax)Cu2Ge2 follows the theoretical prediction based on the molecular field calculation for the S=1/2 resonant level model.</p>