Materializing Rival Ground States in the Barlowite Family of Kagome Magnets: Quantum Spin Liquid, Spin Ordered, and Valence Bond Crystal States
Rebecca W. Smaha, Wei He, Jack Mingde Jiang, JiaJia Wen, Yi-Fan Jiang, John P. Sheckelton, Charles J. Titus, Suyin Grass Wang, Yu-Sheng Chen, Simon J. Teat, Adam A. Aczel, Yang Zhao, Guangyong NMN Xu, Jeffrey W. Lynn, Hong-Chen Jiang, Young S. Lee
Quantum magnet display exotic phases that may be strongly influenced by small differences in structure and composition. Comprehensive structural and magnetic measurements (involving x-ray scattering, neutron scattering, and thermodynamic techniques) were performed on newly synthesized variants of barlowite (Cu4(OH)6FBr) and Zn-substituted barlowite. In contrast to orthorhombic Pnma barlowite, a novel single crystalline variant of barlowite has been synthesized with a less drastic symmetry lowering to hexagonal P63/m. The lesser amount of symmetry breaking results in an overall smaller ordered moment compared to orthorhombic barlowite, moving the hexagonal sample closer to a quantum spin liquid ground state. Sizable single crystals of Zn-substituted barlowite (Cu3.44Zn0.56(OH)6FBr) were successfully grown, and no structural transition is observed down to T=0.1 K, consistent with a quantum spin liquid ground state. The magnetic response is compared to Cu3.05Zn0.95(OH)FBr (powder) and herbertsmithite (powder and crystal). These samples span a spectrum of quantum spin liquidness, allowing this exotic ground state to be probed systematically.