# Coexistence of magnetic order and persistent spin dynamics in a quantum kagome antiferromagnet with no intersite mixing

## TL;DR

This study reveals that the quantum kagome antiferromagnet YCu$_3$(OH)$_6$Cl$_3$ exhibits bulk magnetic order below 15 K, with unconventional features such as coexistence of order and fluctuations, challenging previous assumptions of a quantum spin liquid state.

## Contribution

The paper provides the first evidence of magnetic order in a nearly perfect kagome lattice compound, demonstrating complex coexistence of order and persistent spin dynamics.

## Key findings

- Magnetic order observed below 15 K in YCu$_3$(OH)$_6$Cl$_3$
- Unconventional coexistence of ordered and paramagnetic states
- Persistent spin dynamics at very low temperatures

## Abstract

One of the key questions concerning frustrated lattices that has lately emerged is the role of disorder in inducing spin-liquid-like properties. In this context, the quantum kagome antiferromagnets YCu$_3$(OH)$_6$Cl$_3$, which has been recently reported as the first geometrically perfect realization of the kagome lattice with negligible magnetic/non-magnetic intersite mixing and a possible quantum-spin-liquid ground state, is of particular interest. However, contrary to previous conjectures, here we show clear evidence of bulk magnetic ordering in this compound below $T_N=15$\,K by combining bulk magnetization and heat capacity measurements, and local-probe muon spin relaxation measurements. The magnetic ordering in this material is rather unconventional in several respects. Firstly, a crossover regime where the ordered state coexists with the paramagnetic state extends down to $T_N/3$ and, secondly, the fluctuation crossover is shifted far below $T_N$. Moreover, a reduced magnetic-entropy release at $T_N$ and persistent spin dynamics that is observed at temperatures as low as $T/T_N=1/300$ could be a sign of emergent excitations of correlated spin-loops or, alternatively, a sign of fragmentation of each magnetic moment into an ordered and a fluctuating part.