Regensburg 2025 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 26: Ultrafast Magnetization Effects I
MA 26.12: Vortrag
Mittwoch, 19. März 2025, 18:00–18:15, H16
Heterogenity of the laser-induced magneto-structural phase transition in FeRh revealed by ultrafast x-ray diffraction — •Maximilian Mattern1, Jan-Etinne Pudell2, Vojtech Uhlir3, Jon Ander Arregi3, Angel Rodriguez-Fernandez2, Roman Shayduk2, Wonhyuk Jo2, Anders Madsen2, and Daniel Schick1 — 1Max-Born-Institut, Germany — 2European XFEL, Germany — 3CEITEC BUT, Czech Republic
Laser-induced heterogeneities play an important role for ultrafast dynamics especially of first-order phase transitions due to the phase co-existence during nucleation. However, their probing on picosecond time and nanometer length scales is challenging.
We use time-resolved x-ray diffraction to reveal the transient nanoscale heterogeneity of the laser-induced first-order antiferromagnetic (AFM) to ferromagnetic (FM) phase transition in FeRh that is accompanied by a lattice expansion. Utilizing the good reciprocal space and femtosecond time-resolution of the MID instrument at the European X-ray Free-electron laser, we individually track the picosecond shifts of the structural AFM and FM Bragg peak. The integral of the latter quantifies the transient fraction of the FeRh layer that is in the FM phase, and the signatures of the propagating picosecond strain pulses in the shift of both Bragg peaks reveal its spatial distribution. Our results can distinguish between different nucleation scenarios and reveal that the FM phase nucleates as laterally separated columns through the photoexcited near-surface region, finally forming a closed FM layer at the surface of the inhomogeneously excited FeRh film.
Keywords: ultrafast x-ray diffraction; phase transition; ultrafast magnetism; picosecond ultrasonics; FeRh