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MA: Fachverband Magnetismus

MA 23: Focus Session: Magneto-Transport and Magneto-Optics of Higher Orders in Magnetization I

MA 23.5: Invited Talk

Wednesday, March 19, 2025, 11:15–11:45, H20

electrical and optical detection of the multipolar structure in the magnetization space — •Dazhi Hou — University of Science and Technology of China, Hefei, China

The anomalous Hall effect (AHE) in ferromagnetic materials has traditionally been understood to originate from a dipolar magnetization, with the effect typically showing sensitivity to out-of-plane magnetization. In contrast, we present compelling evidence that the AHE fundamentally arises from multipolar contributions to the magnetization. This discovery enables the observation of AHE under in-plane magnetization in cubic ferromagnets such as iron and nickel, challenging the conventional view. The magnitudes of these multipoles align with theoretical predictions from our recently proposed multipolar structure of Berry curvature in magnetization space. Notably, the octupole term can dominate the AHE in certain conditions, as observed in a van der Waals ferromagnet. Furthermore, we introduce a novel MOKE geometry that detects both the magnitude and direction of the perpendicular magnetization component, enabled by the multipolar structure of Berry curvature. This orthogonal MOKE geometry reveals unique angle-dependent behaviors, providing a direct probe of the magnetization multipoles at optical frequency. Our findings offer new insights into the quantum geometry of magnetization and open new avenues for probing magnetic orders across both electrical and optical domains, offering a unified framework for the study of multipolar magnetization in the context of Berry curvature.

Keywords: Berry curvature; anomalous Hall effect; Magneto-optical Kerr effect; magnetization multipolar

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