Event Details

Maciej Dąbrowski, University of Exeter, joins us for a seminar on Kerr imaging of laser-induced manipulation of magnetic domains in semiconducting and insulating magnets

Over the past decade, lasers have emerged as powerful tools for controlling electron spin through optically driven thermal and electronic excitations. Among experimental techniques, the magneto-optical Kerr effect (MOKE) is a particularly effective method for probing laser-induced magnetisation dynamics with high temporal and spatial resolution.

In this talk, I demonstrate how laser-induced magnetic manipulation can be achieved and visualised using Kerr microscopy in a range of semiconducting and insulating magnetic systems. I first focus on two-dimensional (2D) van der Waals (vdW) magnets, showing that integrating a thin CrI₃ flake with a WSe₂ monolayer enables both helicity-dependent and helicity-independent all-optical switching. This behaviour is attributed to spin-dependent charge transfer across the CrI₃/WSe₂ interface occurring on femtosecond timescales, enabling ultrafast control of magnetic order.

I then show how optical pumping induces complex spin textures in the semiconducting ferromagnet Cr₂Ge₂Te₆, including reversible transformations between stripe and bubble/skyrmion phases. Time-resolved beam-scanning Kerr microscopy reveals thickness-dependent remagnetisation dynamics, with reduced thickness enhancing heat dissipation to the substrate and shortening magnetisation recovery times from nanoseconds to hundreds of picoseconds. The low cross-plane thermal conductivity of Cr₂Ge₂Te₆ further enables recovery of the original domain structure even after a complete loss of magnetic order in the uppermost layers.

Finally, I demonstrate that magneto-optical birefringence can be used to image fully compensated antiferromagnetic domains in thin epitaxial CoO and NiO films. By coupling these insulating antiferromagnets to adjacent metallic layers, sub-bandgap optical excitation drives ultrafast demagnetisation via hot-electron transfer. Optical pumping modifies the antiferromagnetic domain structure and, under specific conditions, enables partial domain switching by sweeping the laser beam across the sample surface along the Néel vector.

[1] M. Dąbrowski, et al. Nat. Commun. 13, 5976, (2022).

[2] M. Khela, M. Dąbrowski, et al. Nat. Commun. 14, 1378 (2023).

[3] M. Dąbrowski, et al. Nat. Commun. 16, 2797 (2025).

About the speaker:

Maciej is a Senior Lecturer at the University of Exeter. His research interests span magnetism, 2D materials, plasmonics, time-resolved microscopy, quantum technologies, and surface physics. Previously, he worked as a postdoc at the University of Pittsburgh, , United States. He did his PhD in Max Planck Institute of Microstructure Physics, Halle, Germany.