Dresden 2020 – scientific programme
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MA: Fachverband Magnetismus
MA 52: Quantum Magnets and Molecular Magnets (joint session TT/MA)
MA 52.7: Talk
Thursday, March 19, 2020, 17:00–17:15, HSZ 304
Y-, La- and Lu-Agardite, preparation, crystal structure, vibrational and low-dimensional magnetic properties — •Aleksandr M. Golubev1, Eva Brücher1, Armin Schulz1, Reinhard K. Kremer1, Robert Glaum2, and Myung-Hwan Whangbo3 — 1Max-Planck-Institut für Festkörperforschung, 70569 Stuttgart, Germany — 2Institut für Anorganische Chemie, Universität Bonn, 53121 Bonn, Germany — 3Department of Chemistry North Carolina State University Raleigh, North Carolina 27695-8204, USA
We have prepared polycrystalline samples of Y, La- and Lu-agardite with composition RECu6(OH)6(AsO4)3 · n H2O (RE = Y, La, Lu; n ≈ 3) and characterized their structural and vibrational properties as well as the magnetic behavior of the Cu2+ entities. The arsenates RECu6(OH)6(AsO4)3 · n H2O (RE = Y, La, Lu; n ≈ 3) are isostructural with the mineral mixite and crystallize with a hexagonal structure which contains ribbons of edge-sharing [CuO5] square-pyramids extending along the hexagonal axis. They interconnect via (AsO4)3− groups to form hexagonal tubes of about 10 Å inner diameter. Such zeolite-like tubes host water molecules, which can be reversibly removed at moderate temperature (≈ 100 oC). Like in mixite the Cu2+ cations in RECu6(OH)6(AsO4)3 · n H2O (RE = Y, La, Lu; n ≈ 3) exhibit low-dimensional antiferromagnetic properties the character of which is subject to changes in the Cu-O-Cu bonding distances and bonding angles due to the lanthanide contraction. DFT calculations indicate that the strongest spin exchange pathways couple the Cu2+ S=1/2 magnetic moments predominantly within the hexagonal tubes.