[Seminar] Exploring a New Family of S = ½ Kagomé Antiferromagnets

Speaker

Dr Lucy Clark, School of Chemistry, University of Birmingham

Title

Exploring a New Family of S = ½ Kagomé Antiferromagnets

Abstract

Materials constructed from kagomé layers of antiferromagnetically coupled S = ½ moments are highly prized as they offer a unique opportunity to explore elusive quantum spin liquid (QSL) states.[1] Recently, the Cu2+-based mineral known as Zn-doped barlowite, ZnCu3(OH)6FBr, has shown promise as a new realisation of the QSL state.[2] Despite this interest, the crystal and magnetic structures of the parent material barlowite, Cu4(OH)6FBr, are poorly understood with several conflicting reports in the literature.[3-5] In this seminar, I will introduce these developments in the field of highly frustrated magnetism before presenting our comprehensive neutron diffraction studies of barlowite. In doing so, I will discuss the intriguing structural phase transition we observe in this material at T = 250 K, and clarify the nature of the magnetic ground state below TN = 15 K.[6] I will also discuss our efforts to control the nature of the structural phase transition within a new family compounds through exchange of the halide ions in barlowite. In addition, I will show that we can tune the magnetic ground state of barlowite from antiferromagnetic order to quantum disorder upon Zn-doping though muon spectroscopy measurements supported by density-functional theory.[7]

[1] Broholm et al., Science 367, 263 (2020)
[2] Han, Singleton, Schlueter, Phys. Rev. Lett. 113, 227203 (2014)
[3] Feng et al., Phys. Rev. B 98, 155127 (2018)
[4] Pasco et al., Phys. Rev. Mater. 2, 0444061 (2018)
[5] Smaha et al., J. Solid State Chem. 268, 123-129 (2018)
[6] Tustain et al., Phys. Rev. Mater. 2, 111405(R) (2018)
[7] Tustain et al., npj Quantum Materials 5, 74 (2020)

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