Dresden 2026 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 26: Transport in Materials: Diffusion, Charge, or Heat Conduction I

MM 26.3: Talk

Wednesday, March 11, 2026, 16:15–16:30, SCH/A216

Coupled Spin–Orbital–Lattice Interactions in FeO: A DFT+U and Heisenberg Analysis — •Hao Chen, Christoph Freysoldt, Mira Todorova, and Jörg Neugebauer — Max-Planck-Institut für Nachhaltige Materialien GmbH, Düsseldorf, Germany

Wüstite (FeO) is a prototypical correlated oxide where spin, orbital, and lattice degrees of freedom are intricately coupled. In addition, significant deviations from stoichiometry can occur via oxygen vacancies and Fe²⁺/Fe³⁺ mixed valency. Local lattice distortions and orbital reorientations around such defects can modify magnetic exchange pathways and thus the defect formation energies. Using DFT+U, we investigate how the orbital orientation in Fe²⁺ correlates with structural strain and magnetic interactions. Our results reveal a well-defined correlation between the minority-spin t_2g occupation and the rhombohedral distortion parameter, giving rise to four distinct symmetry-broken orbital states. By mapping total-energy differences between these orbital configurations onto an effective Heisenberg model, we show that the exchange constants are sensitive to orbital orientation, evidencing strong superexchange–orbital coupling. This framework provides quantitative insight into the competition between Jahn–Teller-like lattice distortions and anisotropic magnetic exchange arising from orbital orientation. Building on this, the study provides a unified DFT+U-based picture of spin–orbital–lattice coupling in FeO and establishes a consistent energetic framework for incorporating spin and orbital effects into defect calculations.

Keywords: FeO; Spin–orbital–lattice coupling; DFT+U; Orbital orientation