Regensburg 2025 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

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

MA 23.7: Vortrag

Mittwoch, 19. März 2025, 12:00–12:15, H20

Magnetic polymorphism in 2D layered antiferromagnets — •Shiwei Wu — Department of Physics, Fudan University

Polymorphism, commonly denoting the variety of molecular or crystal structures, is a vital element in many natural science disciplines. In van der Waals layered antiferromagnets, a new type of magnetic polymorphism is allowed by having multiple layer-selective magnetic structures with the same total magnetization. However, resolving and manipulating such magnetic polymorphs remain a great challenge. In this talk, I will report the use of phase-resolved magnetic second-harmonic generation microscopy to elucidate such magnetic polymorphism in the 2D semiconducting layered antiferromagnet CrSBr, and demonstrate how the magnetic polymorphs can be deterministically switched in an unprecedented layer-selective manner. With the nonlinear magneto-optical technique unveiling the magnetic symmetry information through the amplitude and phase of light, we could unambiguously resolve the polymorphic spin-flip transitions in CrSBr bilayers and tetralayers. Remarkably, the deterministic routing of polymorphic transitions originates from the breaking of energy degeneracy via a magnetic layer-sharing effect: the spin-flip transitions in a tetralayer are governed by the laterally extended bilayer, which acts as a *control bit*. We envision such controllable magnetic polymorphism to be ubiquitous for van der Waals layered antiferromagnets, and could lead to conceptually new design and construction of spintronic and opto-spintronic devices for probabilistic computation and neuromorphic engineering.

Keywords: Magneto-Optics; Second harmonic generation; Symmetry; 2D magnet; CrSBr