Regensburg 2019 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 13: Frustrated Magnets - General 1 (joint session TT/MA)
MA 13.8: Vortrag
Dienstag, 2. April 2019, 11:30–11:45, Theater
Frustrated magnetism of S=5/2 moments on a coupled triangular lattice in Cs3Fe2Br9 — •Daniel Brüning1, Tobias Fröhlich1, Markus Braden1, Ladislav Bohatý2, Petra Becker2, and Thomas Lorenz1 — 1II. Physikalisches Institut, Universität zu Köln, Deutschland — 2Abteilung Kristallographie, Institut für Geologie und Mineralogie, Universität zu Köln, Deutschland
Cs3Fe2Br9 is a hexagonal material consisting of Fe3+ ions with S=5/2 in face-sharing Fe2Br9 bi-octahedra, which form hexagonal double layers of the Fe ions. The triangular arrangement of the magnetic ions in the individual layers causes magnetic frustration. The type of magnetic ground state depends on the ratio between the magnetic exchange couplings: the intradimer coupling J, the intralayer (or in-plane) coupling Jp, and the interlayer coupling Jc. The magnetic ground state of Cs3Fe2Br9 is not a singlet-dimer state as in isostructural Cs3Cr2Br9 and Cs3Cr2Cl9, but there is evidence for antiferromagnetic order with TN = 13.5 K. However, our measurements up to 17 T on large single crystals reveal a very unusual magnetic field vs. temperature phase diagram. For an in-plane field, we find linear M(H) curves, whereas a field H∥c causes multiple phase transitions including a magnetization plateau of 1/3 Msat = 10µB. Neutron diffraction resolved the magnetic structure of two phases which indicate an increasing intralayer coupling. Additionally, we present pulsed-field magnetization measurements revealing further transitions, before reaching saturation around 40 T for H∥c.
This work was supported by the DFG through CRC 1238.