Regensburg 2016 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 66: Magnetic Heusler Materials, Semimetals und Oxides
(Joint session of MA and TT organized by MA)

TT 66.1: Vortrag

Donnerstag, 10. März 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 Yan^1,2, 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.