TY - JOUR A1 - Mattern, M. A1 - Pudell, Jan-Etienne A1 - Laskin, G. A1 - von Reppert, A. A1 - Bargheer, Matias T1 - Analysis of the temperature- and fluence-dependent magnetic stress in laser-excited SrRuO3 JF - Structural Dynamics N2 - 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 Grüneisen 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. KW - Thin films KW - Thermodynamic properties KW - Bragg peak KW - Ultrafast X-ray diffraction KW - Thermal effects KW - Phonons KW - Magnetism KW - Lattice dynamics KW - Lasers KW - Perovskites Y1 - 2020 U6 - https://doi.org/10.1063/4.0000072 SN - 2329-7778 ER - TY - JOUR A1 - von Reppert, Alexander A1 - Willig, Lisa A1 - Pudell, Jan-Etienne A1 - Roessle, M. A1 - Leitenberger, Wolfram A1 - Herzog, Marc A1 - Ganss, F. A1 - Hellwig, O. A1 - Bargheer, Matias T1 - Ultrafast laser generated strain in granular and continuous FePt thin films JF - Applied physics letters N2 - We employ ultrafast X-ray diffraction to compare the lattice dynamics of laser-excited continuous and granular FePt films on MgO (100) substrates. Contrary to recent results on free-standing granular films, we observe in both cases a pronounced and long-lasting out-of-plane expansion. We attribute this discrepancy to the in-plane expansion, which is suppressed by symmetry in continuous films. Granular films on substrates are less constrained and already show a reduced out-of-plane contraction. Via the Poisson effect, out-of-plane contractions drive in-plane expansion and vice versa. Consistently, the granular film exhibits a short-lived out-of-plane contraction driven by ultrafast demagnetization which is followed by a reduced and delayed expansion. From the acoustic reflections of the observed strain waves at the film-substrate interface, we extract a 13% reduction of the elastic constants in thin 10 nm FePt films compared to bulk-like samples. (C) 2018 Author(s). Y1 - 2018 U6 - https://doi.org/10.1063/1.5050234 SN - 0003-6951 SN - 1077-3118 VL - 113 IS - 12 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Sander, Mathias A1 - Herzog, Marc A1 - Pudell, Jan-Etienne A1 - Bargheer, Matias A1 - Weinkauf, N. A1 - Pedersen, M. A1 - Newby, G. A1 - Sellmann, J. A1 - Schwarzkopf, J. A1 - Besse, V. A1 - Temnov, V. V. A1 - Gaal, P. T1 - Spatiotemporal Coherent Control of Thermal Excitations in Solids JF - Physical review letters N2 - X-ray reflectivity measurements of femtosecond laser-induced transient gratings (TG) are applied to demonstrate the spatiotemporal coherent control of thermally induced surface deformations on ultrafast time scales. Using grazing incidence x-ray diffraction we unambiguously measure the amplitude of transient surface deformations with sub-angstrom resolution. Understanding the dynamics of femtosecond TG excitations in terms of superposition of acoustic and thermal gratings makes it possible to develop new ways of coherent control in x-ray diffraction experiments. Being the dominant source of TG signal, the long-living thermal grating with spatial period. can be canceled by a second, time-delayed TG excitation shifted by Lambda/2. The ultimate speed limits of such an ultrafast x-ray shutter are inferred from the detailed analysis of thermal and acoustic dynamics in TG experiments. Y1 - 2017 U6 - https://doi.org/10.1103/PhysRevLett.119.075901 SN - 0031-9007 SN - 1079-7114 VL - 119 SP - 102 EP - 110 PB - American Physical Society CY - College Park ER - TY - GEN A1 - Pavlenko, Elena S. A1 - Sander, Mathias A1 - Mitzscherling, Steffen A1 - Pudell, Jan-Etienne A1 - Zamponi, Flavio A1 - Rössle, Matthias A1 - Bojahr, Andre A1 - Bargheer, Matias T1 - Azobenzene – functionalized polyelectrolyte nanolayers as ultrafast optoacoustic transducers N2 - We introduce azobenzene-functionalized polyelectrolyte multilayers as efficient, inexpensive optoacoustic transducers for hyper-sound strain waves in the GHz range. By picosecond transient reflectivity measurements we study the creation of nanoscale strain waves, their reflection from interfaces, damping by scattering from nanoparticles and propagation in soft and hard adjacent materials like polymer layers, quartz and mica. The amplitude of the generated strain ε ∼ 5 × 10−4 is calibrated by ultrafast X-ray diffraction. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 297 Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-101996 VL - 8 SP - 13297 EP - 13302 ER - TY - JOUR A1 - Pudell, Jan-Etienne A1 - Maznev, A. A. A1 - Herzog, Marc A1 - Kronseder, M. A1 - Back, Christian H. A1 - Malinowski, Gregory A1 - von Reppert, Alexander A1 - Bargheer, Matias T1 - Layer specific observation of slow thermal equilibration in ultrathin metallic nanostructures by femtosecond X-ray diffraction JF - Nature Communications N2 - 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. Y1 - 2018 U6 - https://doi.org/10.1038/s41467-018-05693-5 SN - 2041-1723 VL - 9 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Sarhan, Radwan Mohamed A1 - Koopman, Wouter-Willem Adriaan A1 - Pudell, Jan-Etienne A1 - Stete, Felix A1 - Rössle, Matthias A1 - Herzog, Marc A1 - Schmitt, Clemens Nikolaus Zeno A1 - Liebig, Ferenc A1 - Koetz, Joachim A1 - Bargheer, Matias T1 - Scaling up nanoplasmon catalysis BT - the role of heat dissipation JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - Nanoscale heating by optical excitation of plasmonic nanoparticles offers a new perspective of controlling chemical reactions, where heat is not spatially uniform as in conventional macroscopic heating but strong temperature gradients exist around microscopic hot spots. In nanoplasmonics, metal particles act as a nanosource of light, heat, and energetic electrons driven by resonant excitation of their localized surface plasmon resonance. As an example of the coupling reaction of 4-nitrothiophenol into 4,4′-dimercaptoazobenzene, we show that besides the nanoscopic heat distribution at hot spots, the microscopic distribution of heat dictated by the spot size of the light focus also plays a crucial role in the design of plasmonic nanoreactors. Small sizes of laser spots enable high intensities to drive plasmon-assisted catalysis. This facilitates the observation of such reactions by surface-enhanced Raman scattering, but it challenges attempts to scale nanoplasmonic chemistry up to large areas, where the excess heat must be dissipated by one-dimensional heat transport. KW - Gold KW - Raman spectroscopy KW - Silicon KW - Irradiation KW - Lasers Y1 - 2019 U6 - https://doi.org/10.1021/acs.jpcc.8b12574 SN - 1932-7447 VL - 123 IS - 14 SP - 9352 EP - 9357 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Pudell, Jan-Etienne A1 - Sander, M. A1 - Bauer, R. A1 - Bargheer, Matias A1 - Herzog, M. A1 - Gaál, Peter T1 - Full Spatiotemporal Control of Laser-Excited Periodic Surface Deformations JF - Physical review applied N2 - We demonstrate full control of acoustic and thermal periodic deformations at solid surfaces down to subnanosecond time scales and few-micrometer length scales via independent variation of the temporal and spatial phase of two optical transient grating (TG) excitations. For this purpose, we introduce an experimental setup that exerts control of the spatial phase of subsequent time-delayed TG excitations depending on their polarization state. Specific exemplary coherent control cases are discussed theoretically and corresponding experimental data are presented in which time-resolved x-ray reflectivity measures the spatiotemporal surface distortion of nanolayered heterostructures. Finally, we discuss examples where the application of our method may enable the control of functional material properties via tailored spatiotemporal strain fields. Y1 - 2019 U6 - https://doi.org/10.1103/PhysRevApplied.12.024036 SN - 2331-7019 VL - 12 IS - 2 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Zeuschner, S. P. A1 - Mattern, M. A1 - Pudell, Jan-Etienne A1 - von Reppert, A. A1 - Rössle, M. A1 - Leitenberger, Wolfram A1 - Schwarzkopf, J. A1 - Boschker, J. E. A1 - Herzog, Marc A1 - Bargheer, Matias T1 - Reciprocal space slicing BT - a time-efficient approach to femtosecond x-ray diffraction JF - Structural Dynamics N2 - 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. Y1 - 0202 U6 - https://doi.org/10.1063/4.0000040 SN - 2329-7778 VL - 8 PB - AIP Publishing LLC CY - Melville, NY ER - TY - JOUR A1 - Pudell, Jan-Etienne A1 - von Reppert, Alexander A1 - Schick, D. A1 - Zamponi, F. A1 - Rössle, Matthias A1 - Herzog, M. A1 - Zabel, Hartmut A1 - Bargheer, Matias T1 - Ultrafast negative thermal expansion driven by spin disorder JF - Physical review : B, Condensed matter and materials physics N2 - We measure the transient strain profile in a nanoscale multilayer system composed of yttrium, holmium, and niobium after laser excitation using ultrafast x-ray diffraction. The strain propagation through each layer is determined by transient changes in the material-specific Bragg angles. We experimentally derive the exponentially decreasing stress profile driving the strain wave and show that it closely matches the optical penetration depth. Below the Neel temperature of Ho, the optical excitation triggers negative thermal expansion, which is induced by a quasi-instantaneous contractive stress and a second contractive stress contribution increasing on a 12-ps timescale. These two timescales were recently measured for the spin disordering in Ho [Rettig et al., Phys. Rev. Lett. 116, 257202 (2016)]. As a consequence, we observe an unconventional bipolar strain pulse with an inverted sign traveling through the heterostructure. Y1 - 2019 U6 - https://doi.org/10.1103/PhysRevB.99.094304 SN - 2469-9950 SN - 2469-9969 VL - 99 IS - 9 PB - American Physical Society CY - College Park ER - TY - GEN A1 - Pudell, Jan-Etienne A1 - Maznev, Alexei A1 - Herzog, Marc A1 - Kronseder, M. A1 - Back, Christian A1 - Malinowski, Gregory A1 - von Reppert, Alexander A1 - Bargheer, Matias T1 - Layer specific observation of slow thermal equilibration in ultrathin metallic nanostructures by femtosecond X-ray diffraction T2 - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe N2 - 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. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 797 KW - thin magnetic layers KW - optical-excitation KW - heat-capacity KW - electron KW - gold KW - dynamics Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-426233 SN - 1866-8372 IS - 797 ER - TY - JOUR A1 - Bojahr, Andre A1 - Gohlke, Matthias A1 - Leitenberger, Wolfram A1 - Pudell, Jan-Etienne A1 - Reinhardt, Matthias A1 - von Reppert, Alexander A1 - Rössle, Matthias A1 - Sander, Mathias A1 - Gaal, Peter A1 - Bargheer, Matias T1 - Second Harmonic Generation of Nanoscale Phonon Wave Packets JF - Physical review letters N2 - Phonons are often regarded as delocalized quasiparticles with certain energy and momentum. The anharmonic interaction of phonons determines macroscopic properties of the solid, such as thermal expansion or thermal conductivity, and a detailed understanding becomes increasingly important for functional nanostructures. Although phonon-phonon scattering processes depicted in simple wave-vector diagrams are the basis of theories describing these macroscopic phenomena, experiments directly accessing these coupling channels are scarce. We synthesize monochromatic acoustic phonon wave packets with only a few cycles to introduce nonlinear phononics as the acoustic counterpart to nonlinear optics. Control of the wave vector, bandwidth, and consequently spatial extent of the phonon wave packets allows us to observe nonlinear phonon interaction, in particular, second harmonic generation, in real time by wave-vector-sensitive Brillouin scattering with x-rays and optical photons. Y1 - 2015 U6 - https://doi.org/10.1103/PhysRevLett.115.195502 SN - 0031-9007 SN - 1079-7114 VL - 115 IS - 19 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Pavlenko, Elena S. A1 - Sander, Mathias A1 - Mitzscherling, S. A1 - Pudell, Jan-Etienne A1 - Zamponi, Flavio A1 - Roessle, M. A1 - Bojahr, Andre A1 - Bargheer, Matias T1 - Azobenzene - functionalized polyelectrolyte nanolayers as ultrafast optoacoustic transducers JF - Nanoscale N2 - We introduce azobenzene-functionalized polyelectrolyte multilayers as efficient, inexpensive optoacoustic transducers for hyper-sound strain waves in the GHz range. By picosecond transient reflectivity measurements we study the creation of nanoscale strain waves, their reflection from interfaces, damping by scattering from nanoparticles and propagation in soft and hard adjacent materials like polymer layers, quartz and mica. The amplitude of the generated strain epsilon similar to 5 x 10(-4) is calibrated by ultrafast X-ray diffraction. Y1 - 2016 U6 - https://doi.org/10.1039/c6nr01448h SN - 2040-3364 SN - 2040-3372 VL - 8 SP - 13297 EP - 13302 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - von Reppert, Alexander A1 - Sarhan, Radwan Mohamed A1 - Stete, Felix A1 - Pudell, Jan-Etienne A1 - Del Fatti, N. A1 - Crut, A. A1 - Koetz, Joachim A1 - Liebig, Ferenc A1 - Prietzel, Claudia Christina A1 - Bargheer, Matias T1 - Watching the Vibration and Cooling of Ultrathin Gold Nanotriangles by Ultrafast X-ray Diffraction JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - We study the vibrations of ultrathin gold nanotriangles upon optical excitation of the electron gas by ultrafast X-ray diffraction. We quantitatively measure the strain evolution in these highly asymmetric nano-objects, providing a direct estimation of the amplitude and phase of the excited vibrational motion. The maximal strain value is well reproduced by calculations addressing pump absorption by the nanotriangles and their resulting thermal expansion. The amplitude and phase of the out-of-plane vibration mode with 3.6 ps period dominating the observed oscillations are related to two distinct excitation mechanisms. Electronic and phonon pressures impose stresses with different time dependences. The nanosecond relaxation of the expansion yields a direct temperature sensing of the nano-object. The presence of a thin organic molecular layer at the nanotriangle/substrate interfaces drastically reduces the thermal conductance to the substrate. Y1 - 2016 U6 - https://doi.org/10.1021/acs.jpcc.6b11651 SN - 1932-7447 VL - 120 SP - 28894 EP - 28899 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Sander, Mathias A1 - Koc, A. A1 - Kwamen, C. T. A1 - Michaels, H. A1 - von Reppert, Alexander A1 - Pudell, Jan-Etienne A1 - Zamponi, Flavio A1 - Bargheer, Matias A1 - Sellmann, J. A1 - Schwarzkopf, J. A1 - Gaal, P. T1 - Characterization of an ultrafast Bragg-Switch for shortening hard x-ray pulses JF - Journal of applied physics N2 - We present a nanostructured device that functions as photoacoustic hard x-ray switch. The device is triggered by femtosecond laser pulses and allows for temporal gating of hard x-rays on picosecond (ps) timescales. It may be used for pulse picking or even pulse shortening in 3rd generation synchrotron sources. Previous approaches mainly suffered from insufficient switching contrasts due to excitation-induced thermal distortions. We present a new approach where thermal distortions are spatially separated from the functional switching layers in the structure. Our measurements yield a switching contrast of 14, which is sufficient for efficient hard x-ray pulse shortening. The optimized structure also allows for utilizing the switch at high repetition rates of up to 208 kHz. Published by AIP Publishing. Y1 - 2016 U6 - https://doi.org/10.1063/1.4967835 SN - 0021-8979 SN - 1089-7550 VL - 120 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - von Reppert, Alexander A1 - Pudell, Jan-Etienne A1 - Koc, A. A1 - Reinhardt, M. A1 - Leitenberger, Wolfram A1 - Dumesnil, K. A1 - Zamponi, Flavio A1 - Bargheer, Matias T1 - Persistent nonequilibrium dynamics of the thermal energies in the spin and phonon systems of an antiferromagnet JF - Structural dynamics N2 - We present a temperature and fluence dependent Ultrafast X-Ray Diffraction study of a laser-heated antiferromagnetic dysprosium thin film. The loss of antiferromagnetic order is evidenced by a pronounced lattice contraction. We devise a method to determine the energy flow between the phonon and spin system from calibrated Bragg peak positions in thermal equilibrium. Reestablishing the magnetic order is much slower than the cooling of the lattice, especially around the Neel temperature. Despite the pronounced magnetostriction, the transfer of energy from the spin system to the phonons in Dy is slow after the spin-order is lost. (C) 2016 Author(s). Y1 - 2016 U6 - https://doi.org/10.1063/1.4961253 SN - 2329-7778 VL - 3 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Sander, Mathias A1 - Pudell, Jan-Etienne A1 - Herzog, Marc A1 - Bargheer, Matias A1 - Bauer, R. A1 - Besse, V. A1 - Temnov, V. A1 - Gaal, P. T1 - Quantitative disentanglement of coherent and incoherent laser-induced surface deformations by time-resolved x-ray reflectivity JF - Applied physics letters N2 - We present time-resolved x-ray reflectivity measurements on laser excited coherent and incoherent surface deformations of thin metallic films. Based on a kinematical diffraction model, we derive the surface amplitude from the diffracted x-ray intensity and resolve transient surface excursions with sub-angstrom spatial precision and 70 ps temporal resolution. The analysis allows for decomposition of the surface amplitude into multiple coherent acoustic modes and a substantial contribution from incoherent phonons which constitute the sample heating. Published by AIP Publishing. Y1 - 2017 U6 - https://doi.org/10.1063/1.5004522 SN - 0003-6951 SN - 1077-3118 VL - 111 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Zeuschner, Steffen A1 - Parpiiev, Tymur A1 - Pezeril, Thomas A1 - Hillion, Arnaud A1 - Dumesnil, Karine A1 - Anane, Abdelmadjid A1 - Pudell, Jan-Etienne A1 - Willig, Lisa A1 - Rössle, Matthias A1 - Herzog, Marc A1 - von Reppert, Alexander A1 - Bargheer, Matias T1 - Tracking picosecond strain pulses in heterostructures that exhibit giant magnetostriction JF - Structural Dynamics N2 - 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. KW - Heterostructures KW - Magnetooptical effects KW - Metal oxides KW - Crystal lattices KW - Transition metals KW - Magnetism KW - Ultrafast X-ray diffraction KW - Lasers KW - Bragg peak KW - Phonons Y1 - 2019 U6 - https://doi.org/10.1063/1.5084140 SN - 2329-7778 VL - 6 IS - 2 PB - AIP Publishing LLC CY - Melville, NY ER - TY - GEN A1 - Zeuschner, Steffen A1 - Parpiiev, Tymur A1 - Pezeril, Thomas A1 - Hillion, Arnaud A1 - Dumesnil, Karine A1 - Anane, Abdelmadjid A1 - Pudell, Jan-Etienne A1 - Willig, Lisa A1 - Rössle, Matthias A1 - Herzog, Marc A1 - von Reppert, Alexander A1 - Bargheer, Matias T1 - Tracking picosecond strain pulses in heterostructures that exhibit giant magnetostriction T2 - Postprints der Universität Potsdam : Mathematisch-naturwissenschaftliche Reihe N2 - 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. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 706 KW - Heterostructures KW - Magnetooptical effects KW - Metal oxides KW - Crystal lattices KW - Transition metals KW - Magnetism KW - Ultrafast X-ray diffraction KW - Lasers KW - Bragg peak KW - Phonons Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-428457 SN - 1866-8372 IS - 706 ER - TY - GEN A1 - Mattern, M. A1 - Pudell, Jan-Etienne A1 - Laskin, G. A1 - von Reppert, A. A1 - Bargheer, Matias T1 - Analysis of the temperature- and fluence-dependent magnetic stress in laser-excited SrRuO3 T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - 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 Grüneisen 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. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1144 KW - Thin films KW - Thermodynamic properties KW - Bragg peak KW - Ultrafast X-ray diffraction KW - Thermal effects KW - Phonons KW - Magnetism KW - Lattice dynamics KW - Lasers KW - Perovskites Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-515718 SN - 1866-8372 ER - TY - GEN A1 - Zeuschner, S. P. A1 - Mattern, M. A1 - Pudell, Jan-Etienne A1 - von Reppert, A. A1 - Rössle, M. A1 - Leitenberger, Wolfram A1 - Schwarzkopf, J. A1 - Boschker, J. E. A1 - Herzog, Marc A1 - Bargheer, Matias T1 - Reciprocal space slicing BT - a time-efficient approach to femtosecond x-ray diffraction T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - 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. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1137 Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-499761 SN - 1866-8372 IS - 1137 ER - TY - JOUR A1 - Mattern, Maximilian A1 - Pudell, Jan-Etienne A1 - Dumesnil, Karine A1 - von Reppert, Alexander A1 - Bargheer, Matias T1 - Towards shaping picosecond strain pulses via magnetostrictive transducers JF - Photoacoustics N2 - 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. KW - picosecond ultrasonics KW - magnetostriction KW - ultrafast x-ray diffraction KW - ultrafast photoacoustics KW - nanoscale heat transfer KW - negative thermal expansion Y1 - 2023 U6 - https://doi.org/10.1016/j.pacs.2023.100463 SN - 2213-5979 VL - 30 PB - Elsevier CY - Amsterdam ER - TY - THES A1 - Pudell, Jan-Etienne T1 - Lattice dynamics T1 - Gitterdynamik BT - observed with x-ray diffraction BT - beobachtet mit Röntgenbeugung N2 - In this thesis I summarize my contribution to the research field of ultrafast structural dynamics in condensend matter. It consists of 17 publications that cover the complex interplay between electron, magnon, and phonon subsystems in solid materials and the resulting lattice dynamics after ultrafast photoexcitation. The investigation of such dynamics is necessary for the physical understanding of the processes in materials that might become important in the future as functional materials for technological applications, for example in data storage applications, information processing, sensors, or energy harvesting. In this work I present ultrafast x-ray diffraction (UXRD) experiments based on the optical pump – x-ray probe technique revealing the time-resolved lattice strain. To study these dynamics the samples (mainly thin film heterostructures) are excited by femtosecond near-infrared or visible light pulses. The induced strain dynamics caused by stresses of the excited subsystems are measured in a pump-probe scheme with x-ray diffraction (XRD) as a probe. The UXRD setups used during my thesis are a laser-driven table-top x-ray source and large-scale synchrotron facilities with dedicated time-resolved diffraction setups. The UXRD experiments provide quantitative access to heat reservoirs in nanometric layers and monitor the transient responses of these layers with coupled electron, magnon, and phonon subsystems. In contrast to optical probes, UXRD allows accessing the material-specific information, which is unavailable for optical light due to the detection of multiple indistinguishable layers in the range of the penetration depth. In addition, UXRD facilitates a layer-specific probe for layers buried opaque heterostructures to study the energy flow. I extended this UXRD technique to obtain the driving stress profile by measuring the strain dynamics in the unexcited buried layer after excitation of the adjacent absorbing layers with femtosecond laser pulses. This enables the study of negative thermal expansion (NTE) in magnetic materials, which occurs due to the loss of the magnetic order. Part of this work is the investigation of stress profiles which are the source of coherent acoustic phonon wave packets (hypersound waves). The spatiotemporal shape of these stress profiles depends on the energy distribution profile and the ability of the involved subsystems to produce stress. The evaluation of the UXRD data of rare-earth metals yields a stress profile that closely matches the optical penetration profile: In the paramagnetic (PM) phase the photoexcitation results in a quasi-instantaneous expansive stress of the metallic layer whereas in the antiferromagnetic (AFM) phase a quasi-instantaneous contractive stress and a second contractive stress contribution rising on a 10 ps time scale adds to the PM contribution. These two time scales are characteristic for the magnetic contribution and are in agreement with related studies of the magnetization dynamics of rare-earth materials. Several publications in this thesis demonstrate the scientific progress in the field of active strain control to drive a second excitation or engineer an ultrafast switch. These applications of ultrafast dynamics are necessary to enable control of functional material properties via strain on ultrafast time scales. For this thesis I implemented upgrades of the existing laser-driven table-top UXRD setup in order to achieve an enhancement of x-ray flux to resolve single digit nanometer thick layers. Furthermore, I developed and built a new in-situ time-resolved magneto-optic Kerr effect (MOKE) and optical reflectivity setup at the laser-driven table-top UXRD setup to measure the dynamics of lattice, electrons and magnons under the same excitation conditions. N2 - In dieser Doktoarbeit sind meine Beiträge zum Forschungsgebiet der ltraschnellen Strukturdynamik in kondensierter Materie zusammegefasst. Sie besteht aus 17 Publikationen, welche dieWechselwirkung zwischen Elektron-, Magnon- und Phononsystem in Festkörpern, sowie die dadurch verursachte Gitterdynamik nach ultraschneller optischer Anregung diskutieren. Die Untersuchung dieser Dynamik ist erforderlich für das physikalische Verständnis der Prozesse in Materialien, die in Zukunft als Funktionsmaterialien für technologische Anwendungen, z.B. in der Datenspeicherung und Informationsverarbeitung, sowie bei Sensoren und der Energiegewinnung, wichtig werden könnten. In dieser Arbeit präsentiere ich Experimente, welche ultraschneller Röntgenbeugung (UXRD) als Technik nutzen. Sie basiert auf der Anrege-Abfrage-Technik: Die Dynamik in der Probe (hauptsächlich Dünnfilm-Heterostrukturen) wird durch Femtosekunden-Lichtpulse im nahen Infrarot oder im sichtbaren Bereich angeregt. Die Dehnung des Materials, welche die Spannung (Druck) der angeregten Teilsysteme hervorruft, wird mit Röntgenbeugung als Abfrage gemessen. Während meiner Doktorandentätigkeit habe ich zwei Arten von Aufbauten zur UXRD genutzt: lasergetriebene laborbasierte Röntgenquellen und Synchrotronstrahlungsquellen mit zugehörigen zeitaufgelösten Messinstrumenten. Mit den UXRD-Experimenten kann die gespeicherte Energie unterschiedlicher gekoppelter Teilsysteme, wie Elektronen, Mangonen und Phononen, einer nur wenige Nanometer dicken Schicht gemessen werden. Im Vergleich zu optischenMesstechniken bietet UXRD den Zugriff auf materialspezifische Informationen, die für optisches Licht aufgrund der Detektion mehrerer nicht unterscheidbarer Schichten im Bereich der Eindringtiefe nicht zur Verfügung steht. Darüber hinaus lässt sich mit UXRD eine für optische Detektion verdeckte Schicht als schichtspezifische Sonde nutzen, um den Energietransport zu untersuchen. Dieses Prinzip wurde dazu genutzt, um das treibende Spannungsprofil mittels der Dehnungsdynamik in einer angrenzenden, optisch nicht angeregten Schicht zu messen. Dies ermöglichte die Untersuchung der Dichteanomalie in magnetischen Materialen, die durch den Verlust der magnetischen Ordnung entsteht. Ebenfalls Teil dieser Arbeit ist die Untersuchung von Spannungsprofilen als Quelle von kohärenten akustischen Phononen (Hyperschallwellen). Das raumzeitliche Profil des Spannungsprofils hängt von der Energieverteilung innerhalb der Teilsysteme und ihrer Fähigkeit ab, Energie in Dehnung umzusetzen. Die Auswertung von UXRD Experimenten an Metallen der Seltenen Erden ergab ein Spannungsprofil, dass dem Absorptionsprofil der optischen Anregung entsprach: In der paramagnetischen Phase erzeugte es einen instantanen expansiven Druck, wohingegen in der antiferromagnetischen Phase ein instantaner und ein auf einer 10 ps Zeitskala ansteigender kontrahierender Druck zusätzlich auftritt. Die beiden charakteristischen Zeitskalen in der antiferromagnetischen Phase sind in Übereinstimmung mit verschiedenen Studien der Demagnetisierungsdynamik in den Metallen der Seltenen Erden. Einige Publikationen dieser Arbeit beschäftigen sich mit Feld der aktiven Dehnungskontrolle. Dies ermöglich die Kontrolle von Funktionsmaterialen via Dehnung auf ultraschnellen Zeitskalen. Im Rahmen meiner Doktorandentätigkeit habe ich den lasergetriebenen UXRD Aufbau optimiert, um mit dem hohen Röntgenfluss Experimente mit nur einigen Nanometer dicken Schichten zu ermöglichen. Diese Maschine habe ich um einen zeitaufgelösten Aufbau zur in situ Messung der Reflektivität und Magnetisierungsdynamik mittels magnetooptischem Kerr-Effekt ergänzt. Dies ermöglicht die gleichzeitige Messung von Gitter-, Elektronen- und Magnonendynamik unter derselben Anregebedingung. KW - ultrafast x-ray diffraction KW - ultraschnelle Röntgendiffraktion KW - lattice dynamics KW - Gitterdynamik KW - nanoscale heat transfer KW - nanoskaliger Wärmetransport KW - ultrafast magnetism KW - ultraschneller Magnetimus KW - mechanical and acoustical properties KW - mechanische und akustische Eigenschaften Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-484453 ER - TY - GEN A1 - Mattern, Maximilian A1 - Pudell, Jan-Etienne A1 - Dumesnil, Karine A1 - von Reppert, Alexander A1 - Bargheer, Matias T1 - Towards shaping picosecond strain pulses via magnetostrictive transducers T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - 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. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1321 KW - picosecond ultrasonics KW - magnetostriction KW - ultrafast x-ray diffraction KW - ultrafast photoacoustics KW - nanoscale heat transfer KW - negative thermal expansion Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-588868 SN - 1866-8372 IS - 1321 ER - TY - JOUR A1 - von Reppert, Alexander A1 - Mattern, Maximilian A1 - Pudell, Jan-Etienne A1 - Zeuschner, Steffen Peer A1 - Dumesnil, Karine A1 - Bargheer, Matias T1 - Unconventional picosecond strain pulses resulting from the saturation of magnetic stress within a photoexcited rare earth layer JF - Structural Dynamics N2 - 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. KW - Strain measurement KW - Photoexcitations KW - Crystal lattices KW - Femtosecond lasers KW - Thermal effects KW - Heterostructures KW - Ultrafast X-rays KW - Phonons Y1 - 2020 U6 - https://doi.org/10.1063/1.5145315 SN - 2329-7778 VL - 7 IS - 024303 PB - AIP Publishing LLC CY - Melville, NY ER - TY - GEN A1 - von Reppert, Alexander A1 - Mattern, Maximilian A1 - Pudell, Jan-Etienne A1 - Zeuschner, Steffen Peer A1 - Dumesnil, Karine A1 - Bargheer, Matias T1 - Unconventional picosecond strain pulses resulting from the saturation of magnetic stress within a photoexcited rare earth layer T2 - Postprints der Universität Potsdam : Mathematisch Naturwissenschaftliche Reihe N2 - 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. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 899 KW - Strain measurement KW - Photoexcitations KW - Crystal lattices KW - Femtosecond lasers KW - Thermal effects KW - Heterostructures KW - Ultrafast X-rays KW - Phonons Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-469350 SN - 1866-8372 IS - 899 ER - TY - JOUR A1 - Mattern, Maximilian A1 - von Reppert, Alexander A1 - Zeuschner, Steffen Peer A1 - Pudell, Jan-Etienne A1 - Kühne, F. A1 - Diesing, Detlef A1 - Herzog, Marc A1 - Bargheer, Matias T1 - Electronic energy transport in nanoscale Au/Fe hetero-structures in the perspective of ultrafast lattice dynamics JF - Applied physics letters N2 - We study the ultrafast electronic transport of energy in a photoexcited nanoscale Au/Fe hetero-structure by modeling the spatiotemporal profile of energy densities that drives transient strain, which we quantify by femtosecond x-ray diffraction. This flow of energy is relevant for intrinsic demagnetization and ultrafast spin transport. We measured lattice strain for different Fe layer thicknesses ranging from few atomic layers to several nanometers and modeled the spatiotemporal flow of energy densities. The combination of a high electron-phonon coupling coefficient and a large Sommerfeld constant in Fe is found to yield electronic transfer of nearly all energy from Au to Fe within the first hundreds of femtoseconds. Y1 - 2022 U6 - https://doi.org/10.1063/5.0080378 SN - 0003-6951 SN - 1077-3118 VL - 120 IS - 9 PB - AIP Publishing CY - Melville ER -