Dresden 2020 – wissenschaftliches Programm
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TT 35.8: Vortrag
Mittwoch, 18. März 2020, 11:45–12:00, HSZ 304
Magnetic properties of two sodium ruthenates Na2RuO3 and Na3RuO4 — •Vera P. Bader1, Alexander A. Tsirlin1, Anton Jesche1, Clemens Ritter2, and Philipp Gegenwart1 — 1Center for Electronic Correlations and Magnetism, University of Augsburg, Augsburg, Germany — 2Institut Laue-Langevin, Grenoble, France
Ruthenates show a diversity of magnetic phenomena, e.g. due to transitions between the non-magnetic J = 0 state and excited J = 1 levels in Ru4+  or due to strong Ru-O covalency in the case of Ru5+ . Powder samples of Na2RuO3 and Na3RuO4 were prepared via solid state reactions in a controlled atmosphere. The Ru4+ ions in Na2RuO3 form honeycomb layers which are stacked along the crystallographic c-axis. The measured diffraction pattern could be simulated under the assumption of stacking faults. The inverse susceptibility deviates from the Curie-Weiss behaviour and shows a downward bending in the high temperature region indicating a paramagnetic Van Vleck contribution which would be expected for a J = 0 ground state. In Na3RuO4 the Ru5+ ions form isolated tetramers which are composed of two equilateral triangles. The magnetic susceptibility reveals an antiferromagnetic transition at 30 K while the heat capacity data show two successive phase transitions at 25 K and 28 K. Up to now, the origin of the two phase transitions is not known. Neutron diffraction reveals the absence of symmetry lowering upon both transitions and the development of incommensurate magnetic order.
 J. Chaloupka et al., arXiv:1910.00074 (2019)
 A. Hariki et al., PRB 96 155135 (2017)