Berlin 2024 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 9: Ultrafast Magnetization Effects II
MA 9.6: Vortrag
Montag, 18. März 2024, 16:30–16:45, H 2013
Nucleation and domain growth during the laser-induced metamagnetic phase transition in FeRh identified by UXRD — •Maximilian Mattern1, Steffen Zeuschner1, Jon Ander Arregi2, Vojtěch Uhlíř2, and Matias Bargheer1,3 — 1Institut für Physik und Astronomie, Universität Potsdam, Germany — 2CEITEC BUT, Brno University of Technology, Czech Republic — 3Helmholtz-Zentrum Berlin, Germany
We use time-resolved x-ray diffraction (UXRD) to study the laser-induced first-order antiferromagnetic (AFM) to ferromagnetic (FM) phase transition in FeRh that is accompanied by a gigantic expansion (≈ 0.6%). The laser-induced rise of this expansion accesses the transient FM volume fraction independent of the orientation of the magnetic moment. By comparing two samples with thicknesses below and above the optical penetration depth, we disentangle optically induced nucleation on an intrinsic 8 ps timescale in the near-surface region from the growth of the nucleated FM domains into the depth of the thick inhomogeneously excited FeRh film by slow heat diffusion.
We observe this 8 ps nucleation timescale even in the absence of a transient hot Fermi-distribution of the electrons, when we increase the pump pulse duration up to 10.5 ps. This indicates that hot electrons are not required for driving the phase transition on its intrinsic timescale. Instead, we identify a non-linearity in the laser-induced expansion due to the treshold behaviour of the first-order phase transition, that only starts when the energy successively deposited by the ps-pump pulse overcomes the local critical treshold.
Keywords: ultrafast x-ray diffraction; first-order phase transition; ferromagnetic domains