@article{MatternPudellLaskinetal.2021,
  author    = {Mattern, Maximilian and Pudell, Jan-Etienne and Laskin, Gennadii and Reppert, Alexander von and Bargheer, Matias},
  title     = {Analysis of the temperature- and fluence-dependent magnetic stress in laser-excited SrRuO3},
  series = {Structural dynamics},
  volume    = {8},
  journal   = {Structural dynamics},
  number    = {2},
  publisher = {AIP Publishing LLC},
  address   = {Melville, NY},
  issn      = {2329-7778},
  doi       = {10.1063/4.0000072},
  pages     = {9},
  year      = {2021},
  abstract  = {We use ultrafast x-ray diffraction to investigate the effect of expansive phononic and contractive magnetic stress driving the picosecond strain response of a metallic perovskite SrRuO3 thin film upon femtosecond laser excitation. We exemplify how the anisotropic bulk equilibrium thermal expansion can be used to predict the response of the thin film to ultrafast deposition of energy. It is key to consider that the laterally homogeneous laser excitation changes the strain response compared to the near-equilibrium thermal expansion because the balanced in-plane stresses suppress the Poisson stress on the picosecond timescale. We find a very large negative Gr{\"u}neisen constant describing the large contractive stress imposed by a small amount of energy in the spin system. The temperature and fluence dependence of the strain response for a double-pulse excitation scheme demonstrates the saturation of the magnetic stress in the high-fluence regime.},
  language  = {en}
}
@misc{ZeuschnerMatternPudelletal.2021,
  author    = {Zeuschner, Steffen Peer and Mattern, Maximilian and Pudell, Jan-Etienne and Reppert, Alexander von and R{\"o}ssle, Matthias and Leitenberger, Wolfram and Schwarzkopf, Jutta and Boschker, Jos and Herzog, Marc and Bargheer, Matias},
  title     = {Reciprocal space slicing},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {1137},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-49976},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-499761},
  pages     = {13},
  year      = {2021},
  abstract  = {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 (ω) nor the exit (2θ) diffraction angle is scanned during the strain assessment via x-ray diffraction. Shifts of diffraction peaks on the fixed x-ray area detector originate from an out-of-plane strain within the sample. Quantitative strain assessment requires the determination of a factor relating the observed shift to the change in the reciprocal lattice vector. The factor depends only on the widths of the peak along certain directions in reciprocal space, the diffraction angle of the studied reflection, and the resolution of the instrumental setup. We provide a full theoretical explanation and exemplify the concept with picosecond strain dynamics of a thin layer of NbO2.},
  language  = {en}
}
@article{ZeuschnerMatternPudelletal.2021,
  author    = {Zeuschner, Steffen Peer and Mattern, Maximilian and Pudell, Jan-Etienne and Reppert, Alexander von and R{\"o}ssle, Matthias and Leitenberger, Wolfram and Schwarzkopf, Jutta and Boschker, Jos and Herzog, Marc and Bargheer, Matias},
  title     = {Reciprocal space slicing},
  series = {Structural dynamics},
  volume    = {8},
  journal   = {Structural dynamics},
  number    = {1},
  publisher = {AIP Publishing LLC},
  address   = {Melville, NY},
  issn      = {2329-7778},
  doi       = {10.1063/4.0000040},
  pages     = {10},
  year      = {2021},
  abstract  = {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 (ω) nor the exit (2θ) diffraction angle is scanned during the strain assessment via x-ray diffraction. Shifts of diffraction peaks on the fixed x-ray area detector originate from an out-of-plane strain within the sample. Quantitative strain assessment requires the determination of a factor relating the observed shift to the change in the reciprocal lattice vector. The factor depends only on the widths of the peak along certain directions in reciprocal space, the diffraction angle of the studied reflection, and the resolution of the instrumental setup. We provide a full theoretical explanation and exemplify the concept with picosecond strain dynamics of a thin layer of NbO2.},
  language  = {en}
}
@misc{MatternPudellDumesniletal.2023,
  author    = {Mattern, Maximilian and Pudell, Jan-Etienne and Dumesnil, Karine and Reppert, Alexander von and Bargheer, Matias},
  title     = {Towards shaping picosecond strain pulses via magnetostrictive transducers},
  series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {1321},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-58886},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-588868},
  pages     = {7},
  year      = {2023},
  abstract  = {Using time-resolved x-ray diffraction, we demonstrate the manipulation of the picosecond strain response of a metallic heterostructure consisting of a dysprosium (Dy) transducer and a niobium (Nb) detection layer by an external magnetic field. We utilize the first-order ferromagnetic-antiferromagnetic phase transition of the Dy layer, which provides an additional large contractive stress upon laser excitation compared to its zerofield response. This enhances the laser-induced contraction of the transducer and changes the shape of the picosecond strain pulses driven in Dy and detected within the buried Nb layer. Based on our experiment with rare-earth metals we discuss required properties for functional transducers, which may allow for novel field-control of the emitted picosecond strain pulses.},
  language  = {en}
}
@article{MatternReppertZeuschneretal.2023,
  author    = {Mattern, Maximilian and Reppert, Alexander von and Zeuschner, Steffen Peer and Herzog, Marc and Pudell, Jan-Etienne and Bargheer, Matias},
  title     = {Concepts and use cases for picosecond ultrasonics with x-rays},
  series = {Photoacoustics},
  volume    = {31},
  journal   = {Photoacoustics},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {2213-5979},
  doi       = {10.1016/j.pacs.2023.100503},
  pages     = {22},
  year      = {2023},
  abstract  = {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 Gruneisen parameters stating that the laser-induced stress is proportional to energy density changes in the microscopic subsystems of the solid, i.e., electrons, phonons and spins. The laser-driven strain response can thus serve as an ultrafast proxy for local energy-density and temperature changes, but we emphasize the importance of the nanoscale morphology for an accurate interpretation due to the Poisson effect. The presented experimental use cases encompass ultrathin and opaque metal-heterostructures, continuous and granular nanolayers as well as negative thermal expansion materials, that each pose a challenge to established all-optical techniques.},
  language  = {en}
}
@misc{ReppertMatternPudelletal.2020,
  author    = {Reppert, Alexander von and Mattern, Maximilian and Pudell, Jan-Etienne and Zeuschner, Steffen Peer and Dumesnil, Karine and Bargheer, Matias},
  title     = {Unconventional picosecond strain pulses resulting from the saturation of magnetic stress within a photoexcited rare earth layer},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe},
  number    = {899},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-46935},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-469350},
  pages     = {15},
  year      = {2020},
  abstract  = {Optical excitation of spin-ordered rare earth metals triggers a complex response of the crystal lattice since expansive stresses from electron and phonon excitations compete with a contractive stress induced by spin disorder. Using ultrafast x-ray diffraction experiments, we study the layer specific strain response of a dysprosium film within a metallic heterostructure upon femtosecond laser-excitation. The elastic and diffusive transport of energy to an adjacent, non-excited detection layer clearly separates the contributions of strain pulses and thermal excitations in the time domain. We find that energy transfer processes to magnetic excitations significantly modify the observed conventional bipolar strain wave into a unipolar pulse. By modeling the spin system as a saturable energy reservoir that generates substantial contractive stress on ultrafast timescales, we can reproduce the observed strain response and estimate the time- and space dependent magnetic stress. The saturation of the magnetic stress contribution yields a non-monotonous total stress within the nanolayer, which leads to unconventional picosecond strain pulses.},
  language  = {en}
}
@misc{MatternPudellLaskinetal.2021,
  author    = {Mattern, Maximilian and Pudell, Jan-Etienne and Laskin, G. and Reppert, Alexander von and Bargheer, Matias},
  title     = {Analysis of the temperature- and fluence-dependent magnetic stress in laser-excited SrRuO3},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-51571},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-515718},
  pages     = {11},
  year      = {2021},
  abstract  = {We use ultrafast x-ray diffraction to investigate the effect of expansive phononic and contractive magnetic stress driving the picosecond strain response of a metallic perovskite SrRuO3 thin film upon femtosecond laser excitation. We exemplify how the anisotropic bulk equilibrium thermal expansion can be used to predict the response of the thin film to ultrafast deposition of energy. It is key to consider that the laterally homogeneous laser excitation changes the strain response compared to the near-equilibrium thermal expansion because the balanced in-plane stresses suppress the Poisson stress on the picosecond timescale. We find a very large negative Gr{\"u}neisen constant describing the large contractive stress imposed by a small amount of energy in the spin system. The temperature and fluence dependence of the strain response for a double-pulse excitation scheme demonstrates the saturation of the magnetic stress in the high-fluence regime.},
  language  = {en}
}
@misc{ZeuschnerParpiievPezeriletal.2019,
  author    = {Zeuschner, Steffen Peer and Parpiiev, Tymur and Pezeril, Thomas and Hillion, Arnaud and Dumesnil, Karine and Anane, Abdelmadjid and Pudell, Jan-Etienne and Willig, Lisa and R{\"o}ssle, Matthias and Herzog, Marc and Reppert, Alexander von and Bargheer, Matias},
  title     = {Tracking picosecond strain pulses in heterostructures that exhibit giant magnetostriction},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-naturwissenschaftliche Reihe},
  number    = {706},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-42845},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-428457},
  pages     = {9},
  year      = {2019},
  abstract  = {We combine ultrafast X-ray diffraction (UXRD) and time-resolved Magneto-Optical Kerr Effect (MOKE) measurements to monitor the strain pulses in laser-excited TbFe2/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 TbFe2 surface terminates the sample and a decomposition of the strain wavepacket into an asymmetric bipolar and a unipolar pulse, if a SiO2 glass capping layer covers the excited TbFe2 layer. The inverse magnetostriction of the temporally separated unipolar strain pulses in this sample leads to a MOKE signal that linearly depends on the strain pulse amplitude measured through UXRD. Linear chain model simulations accurately predict the timing and shape of UXRD and MOKE signals that are caused by the strain reflections from multiple interfaces in the heterostructure.},
  language  = {en}
}
@misc{PudellMaznevHerzogetal.2018,
  author    = {Pudell, Jan-Etienne and Maznev, Alexei and Herzog, Marc and Kronseder, M. and Back, Christian and Malinowski, Gregory and Reppert, Alexander von and Bargheer, Matias},
  title     = {Layer specific observation of slow thermal equilibration in ultrathin metallic nanostructures by femtosecond X-ray diffraction},
  series = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe},
  number    = {797},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-42623},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-426233},
  pages     = {7},
  year      = {2018},
  abstract  = {Ultrafast heat transport in nanoscale metal multilayers is of great interest in the context of optically induced demagnetization, remagnetization and switching. If the penetration depth of light exceeds the bilayer thickness, layer-specific information is unavailable from optical probes. Femtosecond diffraction experiments provide unique experimental access to heat transport over single digit nanometer distances. Here, we investigate the structural response and the energy flow in the ultrathin double-layer system: gold on ferromagnetic nickel. Even though the excitation pulse is incident from the Au side, we observe a very rapid heating of the Ni lattice, whereas the Au lattice initially remains cold. The subsequent heat transfer from Ni to the Au lattice is found to be two orders of magnitude slower than predicted by the conventional heat equation and much slower than electron-phonon coupling times in Au. We present a simplified model calculation highlighting the relevant thermophysical quantities.},
  language  = {en}
}
@article{MatternPudellDumesniletal.2023,
  author    = {Mattern, Maximilian and Pudell, Jan-Etienne and Dumesnil, Karine and Reppert, Alexander von and Bargheer, Matias},
  title     = {Towards shaping picosecond strain pulses via magnetostrictive transducers},
  series = {Photoacoustics},
  volume    = {30},
  journal   = {Photoacoustics},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {2213-5979},
  doi       = {10.1016/j.pacs.2023.100463},
  pages     = {7},
  year      = {2023},
  abstract  = {Using time-resolved x-ray diffraction, we demonstrate the manipulation of the picosecond strain response of a metallic heterostructure consisting of a dysprosium (Dy) transducer and a niobium (Nb) detection layer by an external magnetic field. We utilize the first-order ferromagnetic-antiferromagnetic phase transition of the Dy layer, which provides an additional large contractive stress upon laser excitation compared to its zerofield response. This enhances the laser-induced contraction of the transducer and changes the shape of the picosecond strain pulses driven in Dy and detected within the buried Nb layer. Based on our experiment with rare-earth metals we discuss required properties for functional transducers, which may allow for novel field-control of the emitted picosecond strain pulses.},
  language  = {en}
}