Regensburg 2025 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 2: Multiferroics and Magnetoelectric Coupling (joint session MA/KFM)
MA 2.3: Vortrag
Montag, 17. März 2025, 10:00–10:15, H16
Hidden order in Cr2O3 and α-Fe2O3 as a predictor for (anti-)magnetoelectricity — •Xanthe Verbeek1,2, Andrea Urru2,3, and Nicola Spaldin2 — 1Insitut für Physik, Johannes Gutenberg-Universität Mainz, D-55099 Mainz, Germany — 2Materials Department, ETH Zurich, 8093 Zürich, Switzerland — 3Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA
With first-principles calculations of Cr2O3 and α-Fe2O3, we show that the different magnetoelectric effects in these materials result from the ordering of hidden magnetic multipoles. We reveal for the first time anti-ferroically ordered magnetic multipoles in both Cr2O3, and isostructural α-Fe2O3, in which the global inversion symmetry is preserved by the different magnetic dipolar ordering. We can relate each of these multipoles and their ordering to linear, quadratic, and cubic (anti-) magnetoelectric effects, where in an anti-magnetoelectric effect the induced moments are ordered antiferromagnetically in the unit cell. We confirm the predicted induced moments using first-principles calculations, showing the lowest response in α-Fe2O3 a centrosymmetric magnetic material, to be a linear anti-magnetoelectric effect, revealing the presence of the magnetoelectric coupling despite the preserved global inversion symmetry. Our results demonstrate the existence of hidden magnetic multipoles leading to local linear magnetoelectric responses, even in centrosymmetric magnetic materials, and broaden the definition of magnetoelectric materials by including those showing such local magnetoelectric responses.
Keywords: Magnetoelectric; Multipoles; Density functional theory; Antiferromagnets