Magnetic dilution in the triangular lattice antiferromagnet NaYb$_{1-x}$Lu$_{x}$O$_2$

TL;DR

This study investigates how substituting nonmagnetic Lu into NaYbO$_2$ affects its quantum spin liquid state, revealing persistent magnetic fluctuations and suppression of magnetic order, thus supporting the robustness of entangled magnetic networks.

Contribution

It provides experimental insights into the effects of magnetic dilution on a triangular lattice quantum spin liquid candidate, validating models of disorder in such systems.

Findings

Magnetic fluctuations persist up to 15% Lu dilution.

Dilution suppresses field-induced magnetic order.

Low-temperature excitations show a crossover in behavior.

Abstract

The delafossite-like compound NaYbO$_2$ hosts a triangular lattice of Yb$^{3+}$ moments and is a promising candidate for the realization of a quantum spin liquid ground state -- an exotic, quantum-disordered magnetic phase featuring long-range entanglement of spins. Tuning this system away from this quantum-disordered regime toward classical order or spin freezing is a powerful approach to shed light on the nature of the parent ground state. Here we leverage the substitution of nonmagnetic Lu$^{3+}$ onto the Yb$^{3+}$ sites to study the effects of magnetic disorder in NaYbO$_2$ using low-temperature ac susceptibility, heat capacity, and muon spin relaxation ($\mu$SR) measurements. Our $\mu$SR measurements reveal resilient, correlated magnetic fluctuations that persist to at least 15\% dilution, precluding conventional spin freezing and magnetic inhomogeneity. Heat capacity and magnetic susceptibility resolve a rapid suppression of the field-induced ``up-up-down'' magnetic order upon dilution and a crossover in the power-law behavior of the low-temperature magnetic excitations associated with the zero-field quantum disordered ground state. Taken together, these results support the notion of a robust network of entangled moments in NaYbO$_2$, and provides experimental validation of several models of a Heisenberg triangular lattice antiferromagnet in the presence of disorder.