Berlin 2018 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 47: Frustrated Magnets - Iridates and Fe-based Materials
TT 47.9: Vortrag
Mittwoch, 14. März 2018, 11:45–12:00, H 0104
Magnetism in the fcc lattices of K2IrX6 (X=Cl, Br) crystals: Candidate jeff=1/2 Mott insulators — •Nazir Khan1, Danil A. Prishchenko2, Vladimir G. Mazurenko2, Anton Jesche1, and Alexander A. Tsirlin1 — 1EP VI, EKM, Augsburg University, 86159 Augsburg, Germany — 2Ural Federal University, Mira Str. 19, 620002 Ekaterinburg, Russia
Potassium hexahaxoiridates K2Ir4+X6 (X= Cl, Br) are fascinating systems to explore the physics of spin-orbit coupled jeff=1/2 moments on the geometrically frustrated fcc lattice. The structural symmetry of the system and the spin-orbit coupling in the Ir4+ ions allow different anisotropic exchanges besides the isotropic Heisenberg exchange (JH) such as the Kitaev (JK) and off-diagonal (Jγ) exchanges to determine its magnetic ground state. Transport measurement shows highly insulating electronic nature with charge gaps of 0.7 eV and 1.0 eV for the K2IrCl6 and K2IrBr6 compounds, respectively. Magnetization and heat capacity measurements show paramagnetic to antiferromagnetic phase transitions with Néel temperatures TN= 3.1 K and 10.2 K for the K2IrCl6 and K2IrBr6 crystals, respectively, with effective moments close to that predicted theoretically for the jeff=1/2 moment. The field dependence of the magnetization along different crystallographic directions suggests intricate nature of the exchange interactions. The structural and the magneto-electronic phase diagrams show strong dependence on the nature of the halogen ion X− (Cl− and Br−). Magnetism in K2IrCl6 has been discussed in terms of a Heisenberg-Kitaev model.