Magnetic ground state and persistent spin fluctuations in triangular-lattice antiferromagnet NdZnAl$_{11}$O$_{19}$

TL;DR

This study investigates NdZnAl$_{11}$O$_{19}$, a triangular-lattice antiferromagnet, revealing persistent spin fluctuations and no magnetic order down to very low temperatures, indicating potential quantum spin liquid behavior.

Contribution

The paper provides the first comprehensive experimental evidence of persistent spin fluctuations and absence of magnetic order in NdZnAl$_{11}$O$_{19}$, supporting its candidacy as a quantum spin liquid.

Findings

Well-defined $J_{eff}=1/2$ ground state with moderate Ising anisotropy

Persistent spin fluctuations observed below 15 K down to 0.28 K

No magnetic ordering or spin freezing down to 50 mK

Abstract

Rare-earth triangular-lattice magnets serve as an excellent platform for investigating exotic quantum magnetic phenomena. Recently, the hexaaluminate \cmao\ has been proposed to host a $U(1)$ Dirac quantum spin liquid state with dominant Ising anisotropy. Here, we report a systematic study of its analogue, \nzao, employing ac susceptibility, inelastic neutron scattering, and muon spin relaxation measurements. Inelastic neutron scattering measurements establish a well-defined $J_\mathrm{eff}$ = 1/2 ground state with moderate Ising anisotropy ($g_c$ = 4.54, $g_\mathrm{ab}$ = 1.42). Muon spin relaxation measurements reveal persistent fluctuations emerging below $\sim$15\,K, and extending down to at least 0.28 K. AC susceptibility data further indicate an absence of magnetic ordering or spin freezing down to 50\,mK, despite an overall antiferromagnetic interaction with the Curie-Weiss temprature of $-0.42$\,K. These results suggest that \nzao\ is a good candidate material for realizing a quantum spin liquid state.