Berlin 2018 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 47: Frustrated Magnets - Iridates and Fe-based Materials
TT 47.1: Vortrag
Mittwoch, 14. März 2018, 09:30–09:45, H 0104
Dimer formation in hyperhoneycomb iridate β-Li2IrO3 under pressure — •Aleksandra Krajewska1,2, Tomohiro Takayama1,2, Alexandra Gibbs3, Craig Bull3, and Hidenori Takagi1,2 — 11 Institut für Funktionelle Materie und Quantentechnologien, University of Stuttgart, Germany — 2Max-Planck Institute for Solid State Research, Stuttgart, Germany — 3ISIS Facility, Rutherford Appleton Laboratory, Didcot, UK
Honeycomb-based iridates α, β-A2IrO3 (A = Li, Na) are attracting attention because the magnetic coupling between Jeff = 1/2 isospins renders bond-dependent ferromagnetic interaction, providing a possible route for Kitaev quantum spin liquid (QSL). However, these materials order at low temperatures due to the presence of other magnetic couplings. β-Li2IrO3 shows order below 38 K. With increasing pressure, the magnetic order vanishes above 2 GPa and structural transition occurs at around 4 GPa. The driving force of the structural transition and the relevance to the QSL behaviour remains unclear. We studied the crystal structure of β-Li2IrO3 under pressure in detail by neutron diffraction. Above 4 GPa one of the Ir-Ir distances in the hyperhoneycomb network becomes much shorter than the others. The difference between them is 15%, similar to that in honeycomb Li2RuO3 with spin-singlet dimers, suggesting dimer formation in β-Li2IrO3. We argue that the lattice tuning by pressure modifies the balance of multiple magnetic couplings and leads to the likely destruction of Jeff = 1/2 as a consequence of dimerisation.