Emergence of Kondo-assisted N\'eel order in a Kondo necklace model

TL;DR

This paper demonstrates that in a minimal spin-only Kondo necklace model, Kondo interactions can promote magnetic Nel order rather than suppress it, revealing a universal boundary in Kondo physics.

Contribution

The study introduces a Ni-based spin-(1/2,1) Kondo necklace model that isolates quantum spin correlations, showing Kondo coupling can stabilize magnetic order instead of destroying it.

Findings

Kondo coupling mediates effective antiferromagnetic interactions.

Magnetic phase transition and quantum phase transition observed.

Kondo interactions can enhance magnetic order in certain regimes.

Abstract

The interplay between Kondo screening and magnetic order has long been a central issue in the physics of strongly correlated systems. While the Kondo effect has traditionally been understood to suppress magnetism through the formation of local singlets, recent studies suggest that Kondo interactions may enhance magnetic order under certain conditions. However, these scenarios often rely on complex electronic structures, including orbital and charge degrees of freedom, making the essential mechanisms difficult to isolate. Here we report the realization of a spin-(1/2,1) Kondo necklace model in a Ni-based complex-a minimal spin-only analog of the Kondo lattice that isolates quantum spin correlations by eliminating charge degrees of freedom. Thermodynamic measurements identify a magnetic phase transition and a field-induced quantum phase transition. Perturbative analysis reveals that the Kondo coupling mediates effective antiferromagnetic interactions between the spin-1 sites, stabilizing the N\'eel order across the entire chain. Our results establish a universal boundary in Kondo physics, where coupling to spin-1/2 moments yields singlets, but to spin-1 and higher stabilizes magnetic order.