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Abstract:
Iridium(IV) oxides have gained increased attention in recent years owing to the presence of competing spin-orbit coupling and Coulomb interactions, which facilitate the emergence of novel quantum phenomena. In contrast, the electronic structure and magnetic properties of Ir-IV-based molecular materials remain largely unexplored. In this paper, we take a fresh look at an old but puzzling compound, Na2IrCl6, which can be hydrated to form two stable phases with formulas Na2IrCl6 center dot 2H(2)O and Na2IrCl6 center dot 6H(2)O. Their crystal structures are well illustrated based on X-ray powder diffraction data. Magnetic studies reveal that Na2IrCl6 and Na2IrCl6 center dot 2H(2)O are canted antiferromagnets with ordering temperatures of 7.4 and 2.7 K, respectively, whereas Na2IrCl6 center dot 6H(2)O is paramagnetic down to 1.8 K. First-principle calculations on Na2IrCl6 reveal a J(eff) = 1/2 ground state, and the band structures show that Na2IrCl6 is a spin-orbital-induced semiconductor with an indirect gap of about 0.18 eV.
