Publications by authors named "S P Zeuschner"

This review discusses picosecond ultrasonics experiments using ultrashort hard x-ray probe pulses to extract the transient strain response of laser-excited nanoscopic structures from Bragg-peak shifts. This method provides direct, layer-specific, and quantitative information on the picosecond strain response for structures down to few-nm thickness. We model the transient strain using the elastic wave equation and express the driving stress using Grüneisen parameters stating that the laser-induced stress is proportional to energy density changes in the microscopic subsystems of the solid, i.

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An experimental technique that allows faster assessment of out-of-plane strain dynamics of thin film heterostructures via x-ray diffraction is presented. In contrast to conventional high-speed reciprocal space-mapping setups, our approach reduces the measurement time drastically due to a fixed measurement geometry with a position-sensitive detector. This means that neither the incident () nor the exit ( ) diffraction angle is scanned during the strain assessment via x-ray diffraction.

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Invar-behavior occurring in many magnetic materials has long been of interest to materials science. Here, we show not only invar behavior of a continuous film of FePt but also even negative thermal expansion of FePt nanograins upon equilibrium heating. Yet, both samples exhibit pronounced transient expansion upon laser heating in femtosecond x-ray diffraction experiments.

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Article Synopsis
  • Optical excitation of spin-ordered rare earth metals causes competing expansive and contractive stresses within the crystal lattice, influencing lattice behavior.
  • Using ultrafast x-ray diffraction, researchers analyze the strain response in a dysprosium film layered with a metallic structure when subjected to femtosecond laser pulses.
  • The findings reveal that energy transfer to magnetic excitations alters the typical strain wave behavior, leading to unusual unipolar strain pulses and indicating complex interactions within the film's nanolayer.
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We combine ultrafast X-ray diffraction (UXRD) and time-resolved Magneto-Optical Kerr Effect (MOKE) measurements to monitor the strain pulses in laser-excited TbFe/Nb heterostructures. Spatial separation of the Nb detection layer from the laser excitation region allows for a background-free characterization of the laser-generated strain pulses. We clearly observe symmetric bipolar strain pulses if the excited TbFe surface terminates the sample and a decomposition of the strain wavepacket into an asymmetric bipolar and a unipolar pulse, if a SiO glass capping layer covers the excited TbFe layer.

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