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MA: Fachverband Magnetismus
MA 42: Magnetic Heuslers, Half-Metals and Oxides (jointly with TT)
MA 42.1: Talk
Thursday, March 10, 2016, 09:30–09:45, H34
Singular manifestation of square-planar geometry and novel S=3/2 state of a iridate Na4IrO4 — •Sudipta Kanungo1, Binghai Yan1,2, Patrick Merz1, Claudia Felser1, and Martin Jansen3 — 1Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden, Germany — 2Max-Planck-Institut für Physik komplexer Systeme, 01187, Dresden, Germany — 3Max-Planck-Institut für Festkörperforschung, 70569 Stuttgart, Germany
Local environments and valence electron counts primarily determine the electronic states and physical properties of transition metal complexes. For example, square-planar surroundings found in transition oxometalates such as curprates, Nickaltes are usually associated with the d8 or d9 electron configuration. In this work, we address an experimentally observed exotic square-planar mono-oxoanion [IrO4]4− in Na4IrO4 with Ir(IV) in d5 (S=3/2 state) configuration, using ab-initio calculations. On contrary, in its 3d counterpart, Na4CoO4, Co(IV) is in tetrahedral coordination with S=5/2 high spin state. Our ab-initio calculations reveal that the on-site Coulomb interaction U is the essential factor for determining the stability of the local coordination as well as spin state. We find that due to weak Coulomb repulsion of Ir-5d electrons, Na4IrO4 form in a square-planar coordination whereas for Na4CoO4, Co(IV) is in tetrahedral coordination, due to strong electron correlation at 3d Co site. Following the trend from 5d to 3d, we predict that the intermediate 4d material Na4RhO4, if synthesized, may favor tetrahedral coordination but with an S=1/2 low spin state.