Reduction of the ordered-magnetic moment and its relationship to Kondo coherence in Ce$_{1-x}$La$_{x}$Cu$_{2}$Ge$_{2}$

TL;DR

This study investigates how nonmagnetic La dilution suppresses antiferromagnetic order and reduces the magnetic moment in Ce$_{1-x}$La$_{x}$Cu$_{2}$Ge$_{2}$, revealing a quadratic relationship with Kondo coherence temperature.

Contribution

The paper provides detailed neutron diffraction analysis of magnetic suppression in Ce$_{1-x}$La$_{x}$Cu$_{2}$Ge$_{2}$, highlighting the relationship between magnetic moment reduction and Kondo coherence.

Findings

Magnetic Bragg peaks observed for 0.20 ≤ x ≤ 0.75.

Linear decrease of Néel temperature and magnetic moment with La doping.

Quadratic dependence of magnetic moment on Kondo-coherence temperature.

Abstract

The microscopic details of the suppression of antiferromagnetic order in the Kondo-lattice series Ce$_{1-x}$La$_{x}$Cu$_{2}$Ge$_{2}$ due to nonmagnetic dilution by La are revealed through neutron diffraction results for $x=0.20$, $0.40$, $0.75$, and $0.85$. Magnetic Bragg peaks are found for $0.20\le x\le0.75$, and both the N\'{e}el temperature, $T_{\textrm{N}}$, and the ordered magnetic moment per Ce, $\mu$, linearly decrease with increasing $x$. The reduction in $\mu$ points to strong hybridization of the increasingly diluted Ce $4f$ electrons, and we find a remarkable quadratic dependence of $\mu$ on the Kondo-coherence temperature. We discuss our results in terms of local-moment- versus itinerant-type magnetism and mean-field theory, and show that Ce$_{1-x}$La$_{x}$Cu$_{2}$Ge$_{2}$ provides an exceptional opportunity to quantitatively study competing magnetic interactions in a Kondo lattice.