From magnetic order to quantum disorder in the Zn-barlowite series of <i>S</i>=1/2 kagome antiferromagnets



Tustain, Katherine, Ward-O'Brien, Brendan, Bert, Fabrice, Han, Tianheng, Luetkens, Hubertus, Lancaster, Tom, Huddart, Benjamin M, Baker, Peter J and Clark, Lucy ORCID: 0000-0002-6223-3622
(2020) From magnetic order to quantum disorder in the Zn-barlowite series of <i>S</i>=1/2 kagome antiferromagnets. NPJ QUANTUM MATERIALS, 5 (1). 74-.

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Abstract

<jats:title>Abstract</jats:title><jats:p>We report a comprehensive muon spectroscopy study of the Zn-barlowite series of <jats:inline-formula><jats:alternatives><jats:tex-math>$$S=\frac{1}{2}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>S</mml:mi> <mml:mo>=</mml:mo> <mml:mfrac> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:mfrac> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> kagomé antiferromagnets, Zn<jats:sub><jats:italic>x</jats:italic></jats:sub>Cu<jats:sub>4−<jats:italic>x</jats:italic></jats:sub>(OH)<jats:sub>6</jats:sub>FBr, for <jats:italic>x</jats:italic> = 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 <jats:italic>μ</jats:italic>–F and <jats:italic>μ</jats:italic>–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 (<jats:italic>x</jats:italic> = 0), static long-range magnetic order below <jats:italic>T</jats:italic><jats:sub>N</jats:sub> = 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 <jats:italic>x</jats:italic> = 1.0 end-member of the series—in which antiferromagnetic kagomé layers of Cu<jats:sup>2+</jats:sup><jats:inline-formula><jats:alternatives><jats:tex-math>$$S=\frac{1}{2}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>S</mml:mi> <mml:mo>=</mml:mo> <mml:mfrac> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:mfrac> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> moments are decoupled by diamagnetic Zn<jats:sup>2+</jats:sup> 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 <jats:italic>x</jats:italic> &gt; 0.5, which bears resemblance to the dynamical behaviour of the widely studied Zn-paratacamite series that contains the quantum spin liquid candidate herbertsmithite.</jats:p>

Item Type: Article
Divisions: Faculty of Science and Engineering > School of Physical Sciences
Depositing User: Symplectic Admin
Date Deposited: 09 Sep 2021 15:06
Last Modified: 17 Mar 2024 10:30
DOI: 10.1038/s41535-020-00276-4
Open Access URL: https://www.nature.com/articles/s41535-020-00276-4
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URI: https://livrepository.liverpool.ac.uk/id/eprint/3136519