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 - 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 - 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 - Tchoumba Kwamen, Christelle Larodia A1 - Rössle, Matthias A1 - Leitenberger, Wolfram A1 - Alexe, Marin A1 - Bargheer, Matias T1 - Time-resolved X-ray diffraction study of the structural dynamics in an epitaxial ferroelectric thin Pb(Zr0.2Ti0.8)O-3 film induced by sub-coercive fields JF - Applied physics letters N2 - The electric field-dependence of structural dynamics in a tetragonal ferroelectric lead zirconate titanate thin film is investigated under subcoercive and above-coercive fields using time-resolved X-ray diffraction. The domain nucleation and growth are monitored in real time during the application of an external field to the prepoled thin film capacitor. We propose the observed broadening of the in-plane peak width of the symmetric 002 Bragg reflection as an indicator of the domain disorder and discuss the processes that change the measured peak intensity. Subcoercive field switching results in remnant disordered domain configurations. Published under license by AIP Publishing. Y1 - 2019 U6 - https://doi.org/10.1063/1.5084104 SN - 0003-6951 SN - 1077-3118 VL - 114 IS - 16 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Vadilonga, Simone A1 - Zizak, Ivo A1 - Roshchupkin, Dmitry A1 - Evgenii, Emelin A1 - Petsiuk, Andrei A1 - Leitenberger, Wolfram A1 - Erko, Alexei T1 - Observation of sagittal X-ray diffraction by surface acoustic waves in Bragg geometry JF - Journal of applied crystallography N2 - X-ray Bragg diffraction in sagittal geometry on a Y-cut langasite crystal (La3Ga5SiO14) modulated by Lambda = 3 mu m Rayleigh surface acoustic waves was studied at the BESSY II synchrotron radiation facility. Owing to the crystal lattice modulation by the surface acoustic wave diffraction, satellites appear. Their intensity and angular separation depend on the amplitude and wavelength of the ultrasonic superlattice. Experimental results are compared with the corresponding theoretical model that exploits the kinematical diffraction theory. This experiment shows that the propagation of the surface acoustic waves creates a dynamical diffraction grating on the crystal surface, and this can be used for space-time modulation of an X-ray beam. KW - surface acoustic waves KW - optics KW - synchrotron radiation KW - sagittal X-ray diffraction Y1 - 2017 U6 - https://doi.org/10.1107/S1600576717002977 SN - 1600-5767 VL - 50 SP - 525 EP - 530 PB - International Union of Crystallography CY - Chester ER - TY - JOUR A1 - Koc, A. A1 - Reinhardt, M. A1 - von Reppert, Alexander A1 - Rössle, Matthias A1 - Leitenberger, Wolfram A1 - Gleich, M. A1 - Weinelt, M. A1 - Zamponi, Flavio A1 - Bargheer, Matias T1 - Grueneisen-approach for the experimental determination of transient spin and phonon energies from ultrafast x-ray diffraction data: gadolinium JF - Journal of physics : Condensed matter N2 - We study gadolinium thin films as a model system for ferromagnets with negative thermal expansion. Ultrashort laser pulses heat up the electronic subsystem and we follow the transient strain via ultrafast x-ray diffraction. In terms of a simple Grueneisen approach, the strain is decomposed into two contributions proportional to the thermal energy of spin and phonon subsystems. Our analysis reveals that upon femtosecond laser excitation, phonons and spins can be driven out of thermal equilibrium for several nanoseconds. KW - ultrafast KW - x-ray diffraction KW - magnetostriction KW - nonequilibrium KW - spin KW - phonon KW - rare earth Y1 - 2017 U6 - https://doi.org/10.1088/1361-648X/aa7187 SN - 0953-8984 SN - 1361-648X VL - 29 SP - 5884 EP - 5891 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Koc, Azize A1 - Reinhardt, M. A1 - von Reppert, Alexander A1 - Roessle, Matthias A1 - Leitenberger, Wolfram A1 - Dumesnil, K. A1 - Gaal, Peter A1 - Zamponi, Flavio A1 - Bargheer, Matias T1 - Ultrafast x-ray diffraction thermometry measures the influence of spin excitations on the heat transport through nanolayers JF - Physical review : B, Condensed matter and materials physics N2 - We investigate the heat transport through a rare earth multilayer system composed of yttrium (Y), dysprosium (Dy), and niobium (Nb) by ultrafast x-ray diffraction. This is an example of a complex heat flow problem on the nanoscale, where several different quasiparticles carry the heat and conserve a nonequilibrium for more than 10 ns. The Bragg peak positions of each layer represent layer-specific thermometers that measure the energy flow through the sample after excitation of the Y top layer with fs-laser pulses. In an experiment-based analytic solution to the nonequilibrium heat transport problem, we derive the individual contributions of the spins and the coupled electron-lattice system to the heat conduction. The full characterization of the spatiotemporal energy flow at different starting temperatures reveals that the spin excitations of antiferromagnetic Dy speed up the heat transport into the Dy layer at low temperatures, whereas the heat transport through this layer and further into the Y and Nb layers underneath is slowed down. The experimental findings are compared to the solution of the heat equation using macroscopic temperature-dependent material parameters without separation of spin and phonon contributions to the heat. We explain why the simulated energy density matches our experiment-based derivation of the heat transport, although the simulated thermoelastic strain in this simulation is not even in qualitative agreement. Y1 - 2017 U6 - https://doi.org/10.1103/PhysRevB.96.014306 SN - 2469-9950 SN - 2469-9969 VL - 96 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Kwamen, C. A1 - Rössle, Matthias A1 - Reinhardt, M. A1 - Leitenberger, Wolfram A1 - Zamponi, Flavio A1 - Alexe, Marin A1 - Bargheer, Matias T1 - Simultaneous dynamic characterization of charge and structural motion during ferroelectric switching JF - Physical review : B, Condensed matter and materials physics N2 - Monitoring structural changes in ferroelectric thin films during electric field induced polarization switching is important for a full microscopic understanding of the coupled motion of charges, atoms, and domainwalls in ferroelectric nanostructures. We combine standard ferroelectric test sequences of switching and nonswitching electrical pulses with time-resolved x-ray diffraction to investigate the structural response of a nanoscale Pb(Zr0.2Ti0.8)O-3 ferroelectric oxide capacitor upon charging, discharging, and polarization reversal. We observe that a nonlinear piezoelectric response of the ferroelectric layer develops on a much longer time scale than the RC time constant of the device. The complex atomic motion during the ferroelectric polarization reversal starts with a contraction of the lattice, whereas the expansive piezoelectric response sets in after considerable charge flow due to the applied voltage pulses on the electrodes of the capacitor. Our simultaneous measurements on a working device elucidate and visualize the complex interplay of charge flow and structural motion and challenges theoretical modeling. Y1 - 2017 U6 - https://doi.org/10.1103/PhysRevB.96.134105 SN - 2469-9950 SN - 2469-9969 VL - 96 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Reinhardt, Matthias A1 - Koc, Azize A1 - Leitenberger, Wolfram A1 - Gaal, Peter A1 - Bargheer, Matias T1 - Optimized spatial overlap in optical pump-X-ray probe experiments with high repetition rate using laser-induced surface distortions JF - Journal of synchrotron radiation N2 - Ultrafast X-ray diffraction experiments require careful adjustment of the spatial overlap between the optical excitation and the X-ray probe pulse. This is especially challenging at high laser repetition rates. Sample distortions caused by the large heat load on the sample and the relatively low optical energy per pulse lead to only tiny signal changes. In consequence, this results in small footprints of the optical excitation on the sample, which turns the adjustment of the overlap difficult. Here a method for reliable overlap adjustment based on reciprocal space mapping of a laser excited thin film is presented. KW - ultrafast X-ray diffraction KW - nanostructures KW - surface deformation KW - heat diffusion KW - optical pump Y1 - 2016 U6 - https://doi.org/10.1107/S1600577515024443 SN - 1600-5775 VL - 23 SP - 474 EP - 479 PB - International Union of Crystallography CY - Chester ER - TY - JOUR A1 - Roshchupkin, Dmitry A1 - Ortega, Luc A1 - Plotitcyna, Olga A1 - Erko, Alexei A1 - Zizak, Ivo A1 - Vadilonga, Simone A1 - Irzhak, Dmitry A1 - Emelin, Evgenii A1 - Buzanov, Oleg A1 - Leitenberger, Wolfram T1 - Piezoelectric Ca3NbGa3Si2O14 crystal: crystal growth, piezoelectric and acoustic properties JF - Journal of geophysical research : Space physics N2 - Ca3NbGa3Si2O14 (CNGS), a five-component crystal of lanthanum-gallium silicate group, was grown by the Czochralski method. The parameters of the elementary unit cell of the crystal were measured by powder diffraction. The independent piezoelectric strain coefficients d(11) and d(14) were determined by the triple-axis X-ray diffraction in the Bragg and Laue geometries. Excitation and propagation of surface acoustic waves (SAW) were studied by high-resolution X-ray diffraction at BESSY II synchrotron radiation source. The velocity of SAW propagation and power flow angles in the Y-, X-and yxl/+36 degrees-cuts of the CNGS crystal were determined from the analysis of the diffraction spectra. The CNGS crystal was found practically isotropic by its acoustic properties. Y1 - 2016 U6 - https://doi.org/10.1007/s00339-016-0279-1 SN - 0947-8396 SN - 1432-0630 VL - 122 SP - 2803 EP - 2812 PB - Springer CY - New York ER -