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arXiv · 1506.08562

Frustrated magnetic planes with intricate interaction pathways in the mineral langite Cu$_4$(OH)$_6$SO$_4\cdot 2$H$_2$O

Stefan Lebernegg·Alexander A. Tsirlin·Oleg Janson·Günther J. Redhammer·Helge Rosner
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Abstract

Magnetic and crystallographic properties of the mineral langite Cu$_4$(OH)$_6$SO$_4\cdot 2$H$_2$O are reported. Its layered crystal structure features a peculiar spatial arrangement of spin-$\frac12$ Cu$^{2+}$ ions that arises from a combination of corner- and edge-sharing chains. Experimentally, langite orders antiferromagnetically at $T_N\simeq 5.7$ K as revealed by magnetization and specific heat measurements. Despite this very low energy scale of the magnetic transition, langite features significantly stronger couplings on the order of 50-70 K. Half of the Cu$^{2+}$ spins are weakly coupled and saturate around 12T, where the magnetization reaches 0.5$μ_B$/Cu. These findings are rationalized by density-functional band-structure calculations suggesting a complex interplay of frustrated exchange couplings in the magnetic planes. A simplified model of coupled magnetic sublattices explains the experimental features qualitatively. To start from reliable structural data, the crystal structure of langite in the 100-280 K temperature range has been determined by single-crystal x-ray diffraction, and the hydrogen positions were refined computationally.

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Stefan Lebernegg, Alexander A. Tsirlin, Oleg Janson, Günther J. Redhammer, Helge Rosner. 2017-02-09. Frustrated magnetic planes with intricate interaction pathways in the mineral langite Cu$_4$(OH)$_6$SO$_4\cdot 2$H$_2$O. https://doi.org/10.1088/1367-2630%2F18%2F3%2F033020

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