From magnetic order to quantum disorder in the Zn-barlowite series of S = 1/2 kagomé antiferromagnets

Tustain, Katherine; Ward-O’Brien, Brendan; Bert, Fabrice; Han, Tianheng; Luetkens, Hubertus; Lancaster, Tom; Huddart, Benjamin M.; Baker, Peter J.; Clark, Lucy

Abstract

We report a comprehensive muon spectroscopy study of the Zn-barlowite series of S=12 kagomé antiferromagnets, ZnxCu4−x(OH)6FBr, for x = 0.00 to 0.99(1). By combining muon spin relaxation and rotation measurements with state-of-the-art density-functional theory muon-site calculations, we observe the formation of both μ–F and μ–OH complexes in Zn-barlowite. From these stopping sites, implanted muon spins reveal the suppression of long-range magnetic order into a possible quantum spin liquid state upon the increasing concentration of Zn-substitution. In the parent compound (x = 0), static long-range magnetic order below TN = 15 K manifests itself in the form of spontaneous oscillations in the time-dependent muon asymmetry signal consistent with the dipolar fields expected from the calculated muon stopping sites and the previously determined magnetic structure of barlowite. Meanwhile, in the x = 1.0 end-member of the series—in which antiferromagnetic kagomé layers of Cu2+S=12 moments are decoupled by diamagnetic Zn2+ ions—we observe that dynamic magnetic moment fluctuations persist down to at least 50 mK, indicative of a quantum disordered ground state. We demonstrate that this crossover from a static to dynamic magnetic ground state occurs for compositions of Zn-barlowite with x > 0.5, which bears resemblance to the dynamical behaviour of the widely studied Zn-paratacamite series that contains the quantum spin liquid candidate herbertsmithite.

Citation

Tustain, K., Ward-O’Brien, B., Bert, F., Han, T., Luetkens, H., Lancaster, T., Huddart, B. M., Baker, P. J., & Clark, L. (2020). From magnetic order to quantum disorder in the Zn-barlowite series of S = 1/2 kagomé antiferromagnets. npj Quantum Materials, 5(1), Article 74. https://doi.org/10.1038/s41535-020-00276-4

• Journal Article Type: Article
• Acceptance Date: Sep 22, 2020
• Online Publication Date: Oct 23, 2020
• Publication Date: 2020
• Deposit Date: Oct 26, 2020
• Publicly Available Date: Oct 29, 2020
• Journal: npj quantum materials.
• Print ISSN: 2397-4648
• Publisher: Nature Research
• Peer Reviewed: Peer Reviewed
• Volume: 5
• Issue: 1
• Article Number: 74
• DOI: https://doi.org/10.1038/s41535-020-00276-4
• Public URL: https://durham-repository.worktribe.com/output/1259084