From spin liquid to magnetic ordering in the anisotropic kagome Y-Kapellasite Y3Cu9(OH)19Cl8: a single crystal study

TL;DR

This study investigates the magnetic properties of Y3Cu9(OH)19Cl8 single crystals, revealing subtle structural instabilities and a magnetic transition to long-range order, with findings suggesting proximity to a quantum spin liquid phase.

Contribution

The paper provides an improved synthesis method for large single crystals and offers detailed experimental insights into the magnetic phase diagram of an anisotropic kagome system.

Findings

Evidence of structural instabilities at 33K and 13K.

Observation of a magnetic transition to long-range order at 2.1K.

Magnetic interactions place the system near a quantum spin liquid phase.

Abstract

Y3Cu9(OH)19Cl8 realizes an original anisotropic kagome model hosting a rich magnetic phase diagram [M. Hering et al, npj Computational Materials 8, 1 (2022)]. We present an improved synthesis of large phase-pure single crystals via an external gradient method. These crystals were investigated in details by susceptibility, specific heat, thermal expansion, neutron scattering and local muSR and NMR techniques. At variance with polycristalline samples, the study of single crystals gives evidence for subtle structural instabilities at 33K and 13K which preserve the global symmetry of the system and thus the magnetic model. At 2.1K the compound shows a magnetic transition to a coplanar (1/3,1/3) long range order as predicted theoretically. However our analysis of the spin wave excitations yields magnetic interactions which locate the compound closer to the phase boundary to a classical jammed spin liquid phase. Enhanced quantum fluctuations at this boundary may be responsible for the strongly reduced ordered moment of the Cu2+, estimated to be 0.075muB from muSR.