Magnetic ordering of the distorted kagome antiferromagnet Y$_3$Cu$_9$(OH)$_{18}$[Cl$_8$(OH)] prepared via optimal synthesis

TL;DR

This study investigates the magnetic properties of high-purity Y3Cu9(OH)18[Cl8(OH)] crystals, revealing a Néel transition at 11 K and demonstrating that previous non-magnetic behavior was due to impurities, not intrinsic lattice symmetry.

Contribution

The paper provides the first high-purity crystal analysis of Y3Cu9(OH)18[Cl8(OH)] showing magnetic ordering, challenging prior assumptions about its spin-liquid state.

Findings

Identified a Néel transition at 11 K in high-purity crystals.

Impurities in earlier samples caused the absence of magnetic order.

High-quality synthesis reveals intrinsic magnetic ordering.

Abstract

Experimental studies of high-purity kagome-lattice antiferromagnets (KAFM) are of great importance in attempting to better understand the predicted enigmatic quantum spin-liquid ground state of the KAFM model. However, realizations of this model can rarely evade magnetic ordering at low temperatures due to various perturbations to its dominant isotropic exchange interactions. Such a situation is for example encountered due to sizable Dzyaloshinskii-Moriya magnetic anisotropy in YCu$_3$(OH)$_6$Cl$_3$, which stands out from other KAFM materials by its perfect crystal structure. We find evidence of magnetic ordering also in the distorted sibling compound Y$_3$Cu$_9$(OH)$_{18}$[Cl$_8$(OH)], which has recently been proposed to feature a spin-liquid ground state arising from a spatially anisotropic kagome lattice. Our findings are based on a combination of bulk susceptibility, specific heat, and magnetic torque measurements that disclose a N\'eel transition temperature of $T_N=11$~K in this material, which might feature a coexistence of magnetic order and persistent spin dynamics as previously found in YCu$_3$(OH)$_6$Cl$_3$. Contrary to previous studies of single crystals and powders containing impurity inclusions, we use high-purity single crystals of Y$_3$Cu$_9$(OH)$_{18}$[Cl$_8$(OH)] grown via an optimized hydrothermal synthesis route that minimizes such inclusions. This study thus demonstrates that the lack of magnetic ordering in less pure samples of the investigated compound does not originate from the reduced symmetry of spin lattice but is instead of extrinsic origin.