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TT: Fachverband Tiefe Temperaturen
TT 30: Complex Oxides
TT 30.12: Talk
Wednesday, March 29, 2023, 12:30–12:45, HSZ 204
The crucial influence of side groups on magnetic superexchange - a modification of the Goodenough-Kanamori-rules — Dijana Milosavljevic1, Oleg Janson2, Stefan-Ludwig Drechsler2, and •Helge Rosner3 — 1Max-Planck-Institut für Mikrostrukturphysik, 06120 Halle, Germany — 2IFW Dresden, 01069 Dresden, Germany — 3Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden, Germany
According to the famous Goodenough-Kanamori-Anderson rules, the key structural feature that determines the magnetic exchange coupling constant for superexchange in magnetic insulators is the magnetic ion-ligand-magnetic ion bond angle. Here, we demonstrate that this angle is not the only determining factor. An at least equally important influence on the exchange coupling has the presence of side groups attached to the ligands. Applying density functional calculations and subsequently derived realistic parameters for a multiband tight-binding model, we provide a quantitative analysis for the example case of edge-sharing Cu-O chains with bond angles near 90 degrees. We find that a single parameter, the difference in onsite-energies of the ligand orbitals parallel and perpendicular to the Cu-O chain, is at least as important as the bond angle for sign and size of the superexchange. This parameter strongly depends on the position of side groups outside the superexchange pathway. For a fixed bond angle, changes of a side group position, only, can cause changes in the superexchange of several hundred Kelvin and thus dramatic changes in the magnetic properties.