Dresden 2017 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 12: Correlated Electrons: Frustrated Magnets - General 1

TT 12.5: Vortrag

Montag, 20. März 2017, 16:00–16:15, HSZ 03

New kagome systems YCu₃(OH)₆Cl₃ and Ga_xCu_4−x(OH)₆Cl₂ — •Pascal Puphal¹, Michael Bolte¹, Denis Sheptyakov², Andrej Pustogow³, Martin Dressel³, Michael Baenitz⁴, and Cornelius Krellner¹ — ¹Goethe-University Frankfurt am Main — ²Laboratory for Neutron Scattering and Imaging, PSI, Villigen — ³1. PI, Stuttgart University — ⁴MPI-CPfS, Dresden

Herbertsmithite ZnCu₃(OH)₆Cl₂ is a highly frustrated kagomé system, which has an antiferromagnetic superexchange interaction of J = 17 meV, but no long-range order has been observed down to T = 50 mK. We have successfully prepared Ga_xCu_4−x(OH)₆Cl₂, with a three valent ion instead of Zn²⁺, which should lead to a Dirac metal as proposed by I. I. Mazin et. al. [1]. We synthesized powder samples of this compound with different substitution amounts of x < 1. Similar to Zn the increasing Ga amount slowly suppresses the ordering at 6.5 K, but the compound stays insulating which is also reflected in its green colour. We show magnetometry, specific heat as well as optical and local probing data like NMR. The second part of the contribution is about YCu₃(OH)₆Cl₃ which shows a new kapellasite like structure. Using hydrothermal growth we synthesized single crystals of up to 2 x 2 x 0.5 mm. The structure is a slightly distorted kagome layer with two copper positions giving a new two-dimensional frustrated arrangement. The susceptibility as well as specific heat show a weak antiferromagnetic ordering at 2.2 K while the system has a Weiss temperature of -104 K resulting in a frustration coefficient of 50.

[1] I. I. Mazin et al., Nature Communications 5, 4261 (2014)