Reduction of the ordered magnetic moment and its relationship to Kondo coherence inCe1−xLaxCu2Ge2

The microscopic details of the suppression of antiferromagnetic order in the Kondo-lattice series ${\mathrm{Ce}}_{1\ensuremath{-}x}{\mathrm{La}}_x{\mathrm{Cu}}₂{\mathrm{Ge}}₂$ 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 $0.20\ensuremath{\le}x\ensuremath{\le}0.75$, and both the N\'eel temperature ${T}_{\mathrm{N}}$ and the ordered magnetic moment per Ce $\ensuremath{\mu}$ linearly decrease with increasing $x$. The reduction in $\ensuremath{\mu}$ points to strong hybridization of the increasingly diluted Ce $4f$ electrons, and we find a remarkable quadratic dependence of $\ensuremath{\mu}$ 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 ${\mathrm{Ce}}_{1\ensuremath{-}x}{\mathrm{La}}_x{\mathrm{Cu}}₂{\mathrm{Ge}}₂$ provides an exceptional opportunity to quantitatively study the multiple magnetic interactions in a Kondo lattice.