The magnetic interactions in honeycomb iridium oxide compounds are studied using quantum chemical wavefunction-based methods. Mapping the results onto the corresponding effective spin model shows the crucial dependence of the anisotropic magnetic couplings, in particular Kitaev exchange, on the precise position of inter-layer species and on additional geometrical factors such as Ir-O-Ir bond angles and Ir-O bond lengths. While the latter define the actual superexchange path between magnetic centers, the former may come into play through strong out-of-plane polarization of ligand 2p orbitals mediating intersite hopping [1,2].
(1) R. Yadav, R. Ray, M. S. Eldeeb, S. Nishimoto, L. Hozoi, and J. van den Brink, Phys. Rev. Lett. 121, 197203 (2018).
(2) R. Yadav, M. S. Eldeeb, R. Ray, S. Aswartham, M. I.Sturza, S. Nishimoto, J. van den Brink, and L. Hozoi, Chem. Sci. 10, 1866 (2019).