The electronic and magnetic properties of Ba5AlIr2O11 containing Ir-Ir dimers are investigated using the generalized gradient approximation (GGA) and GGA + spin-orbit coupling (SOC) calculations. We found that the strong suppression of the magnetic moment in this compound recently found by Terzic et al. [Phys. Rev. B 91, 235147 (2015)] is not due to charge ordering but is related to the joint effect of the spin-orbit interaction and strong covalency, resulting in the formation of metal-metal bonds. They conspire and act against the intraatomic Hund's rule exchange interaction to reduce total magnetic moment of the dimer. We argue that the same mechanism could be relevant for other 4d and 5d dimerized transition metal compounds.
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This work was supported by the Russian Foundation of the Basic Research via Program 16-32-60070, the National Science Foundation via Grant No. DMR-1265162, the U.S. Civilian Research and Development Foundation (CRDF Global) via Grant No. FSCX-14-61025-0, the Russian President Council on Science through Grant No. MD-916.2017.2, FASO (theme “electron” Grant No. 01201463326), MON (Project 236), and Cologne University via German Excellence Initiative and German Project FOR 1346 (D.I.K.).
Streltsov, Sergey V.; Cao, Gang; and Khomskii, Daniel I., "Suppression of Magnetism in Ba5AlIr2O11: Interplay of Hund's Coupling, Molecular Orbitals, and Spin-Orbit Interaction" (2017). Center for Advanced Materials Faculty Publications. 10.