Regensburg 2025 – scientific programme

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MA: Fachverband Magnetismus

MA 28: Cooperative Phenomena: Spin Structures and Magnetic Phase Transitions

MA 28.8: Talk

Wednesday, March 19, 2025, 17:00–17:15, H19

Magneto-optical spectroscopy on cubic noncollinear antiferromagnet HoCu — •Felix Schilberth^1,2, Marein Rahn³, Andreas Bauer⁴, Christian Pfleiderer⁴, Sándor Bordács², and István Kézsmárki¹ — ¹Lst. für Experimentalphysik V, Universität Augsburg — ²Dept. of Physics, BME Budapest — ³Lst. für Experimentalphysik VI, Universität Augsburg — ⁴Lst. für Experimentalphysik zur Topologie korrelierter Systeme, TU München

Giant anomalous Hall effect (AHE) and magneto-optical Kerr-effect (MOKE) can emerge in magnets with topologically non-trivial electronic bands. Besides extrinsic contributions from scattering of electrons by impurities, two intrinsic contributions are considered. In momentum space, the Berry curvature generated by non-trivial band features like Weyl points or nodal lines can produce resonances in the optical conductivity, leading to AHE in the static limit. On the other hand, noncollinear magnetic texture in the real space can induce topological Hall effect (THE). The separation of all three contributions is a remarkable experimental challenge which typically cannot be solved by magnetotransport experiments alone. Here, we address this question in the itinerant cubic antiferromagnet HoCu where a remarkably large AHE on the order of 10⁶ Ω⁻¹cm⁻¹ was observed. By measuring reflectivity and MOKE, we determine the optical Hall effect spectrum, the finite frequency analog of the AHE. In this quantity, the energy scales provided by the scattering rate or the energy of band degeneracies allow to disentangle the AHE contributions by free carriers from interband resonances, decomposing this remarkable transport response.

Keywords: Magneto-Optical Spectroscopy; Noncollinear Antiferromagnets; Anomalous Hall Effect; Magneto-Optical Kerr Effect