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118 results on '"Dürr, Hermann A."'

105. A Closer Look Into Magnetism: Opportunities With Synchrotron Radiation.

Author

Dürr, Hermann A., Eimüller, Thomas, Elmers, Hans-Joachim, Eisebitt, Stefan, Farle, Michael, Kuch, Wolfgang, Matthes, Frank, Martins, Michael, Mertins, Hans-Christoph, Oppeneer, Peter M., Plucinski, Lukasz, Schneider, Claus M., Wende, Heiko, Wurth, Wilfried, and Zabel, Hartmut

Subjects
*MAGNETISM, *SYNCHROTRON radiation, *OPTICAL polarization, *MAGNETIZATION, *MAGNETIC materials, *X-rays
Abstract

The unique properties of synchrotron radiation, such as broad energy spectrum, variable light polarization, and flexible time structure, have made it an enormously powerful tool in the study of magnetic phenomena and materials. The refinement of experimental techniques has led to many new research opportunities, keeping up with the challenges put up by modern magnetism research. In this contribution, we review some of the recent developments in the application of synchrotron radiation and particularly soft X-rays to current problems in magnetism, and we discuss future perspectives. [ABSTRACT FROM AUTHOR]

Published
2009
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106. Workshop on Ultrafast Time-resolved Soft X-ray Science.

Author

Neeb, Matthias, Wernet, Philippe, Dürr, Hermann, Sauerborn, Markus, and Eberhardt, Wolfgang

Subjects
MEETINGS, GRENZ rays, INTELLECTUAL cooperation, ULTRASHORT laser pulses, X-rays, LASERS, FREE electron lasers
Abstract

This article reports that more than 90 participants from Europe, the U.S. and Japan gathered from April 27 to 29, 2005, in Berlin, Germany, to hold a lively international meeting on time-resolved soft X-ray science. The meeting continued the series of preceding workshops held in 2002 in Napa, California and in 2003 in Montreux, Switzerland. The aim of the workshop was to bring together the existing ultrafast laser community and the emerging ultrafast X-ray community in order lo discuss recent scientific highlights from both fields and to outline new directions for the application of ultrafast X-rays. In turn, it was hoped that this would help define the source characteristics of future ultrafast X-ray sources such as X-ray Free Electron Lasers.

Published
2005
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107. Ultrafast perturbation of magnetic domains by optical pumping in a ferromagnetic multilayer

Author

Iacocca, Ezio, Le Guyader, Loic, Reid, Alexander H, Schlotter, William F, Liu, Tian-Min, Higley, Daniel J, Coslovich, Giacomo, Wandel, Scott F, Tengdin, Phoebe M, Patel, Sheena K K, Shabalin, Anatoly, Hua, Nelson, Hrkac, Stjepan B, Nembach, Hans T, Shaw, Justin M, Montoya, Sergio A, Blonsky, Adam, Gentry, Christian, Hoefer, Mark A, Murnane, Margaret M, Kapteyn, Henry C, Fullerton, Eric E, Shpyrko, Oleg, Dürr, Hermann A, and Silva, T J

Abstract

Ultrafast optical pumping of spatially nonuniform magnetic textures is known to induce far-from-equilibrium spin transport effects. Here, we use ultrafast x-ray diffraction with unprecedented dynamic range to study the laser-induced dynamics of labyrinth domain networks in ferromagnetic CoFe/Ni multilayers. We detected azimuthally isotropic, odd order, magnetic diffraction rings up to 5th order. The amplitudes of all three diffraction rings quench to different degrees within 1.6 ps. In addition, all three of the detected diffraction rings both broaden by 15% and radially contract by 6% during the quench process. We are able to rigorously quantify a 31% ultrafast broadening of the domain walls via Fourier analysis of the order-dependent quenching of the three detected diffraction rings. The broadening of the diffraction rings is interpreted as a reduction in the domain coherence length, but the shift in the ring radius, while unambiguous in its occurrence, remains unexplained. In particular, we demonstrate that a radial shift explained by domain wall broadening can be ruled out. With the unprecedented dynamic range of our data, our results provide convincing evidence that labyrinth domain structures are spatially perturbed at ultrafast speeds under far-from-equilibrium conditions, albeit the mechanism inducing the perturbations remains yet to be clarified.

108. Megahertz-rate Ultrafast X-ray Scattering and Holographic Imaging at the European XFEL

Author

Zhou Hagström, Nanna, Schneider, Michael, Kerber, Nico, Yaroslavtsev, Alexander, Burgos Parra, Erick, Beg, Marijan, Lang, Martin, Günther, Christian M., Seng, Boris, Kammerbauer, Fabian, Popescu, Horia, Pancaldi, Matteo, Neeraj, Kumar, Polley, Debanjan, Jangid, Rahul, Hrkac, Stjepan B., Patel, Sheena K. K., Ovcharenko, Sergei, Turenne, Diego, Ksenzov, Dmitriy, Boeglin, Christine, Pronin, Igor, Baidakova, Marina, von Korff Schmising, Clemens, Borchert, Martin, Vodungbo, Boris, Chen, Kai, Luo, Chen, Radu, Florin, Müller, Leonard, Martínez Flórez, Miriam, Philippi-Kobs, André, Riepp, Matthias, Roseker, Wojciech, Grübel, Gerhard, Carley, Robert, Schlappa, Justine, Van Kuiken, Benjamin, Gort, Rafael, Mercadier, Laurent, Agarwal, Naman, Le Guyader, Loïc, Mercurio, Giuseppe, Teichmann, Martin, Torben Delitz, Jan, Reich, Alexander, Broers, Carsten, Hickin, David, Deiter, Carsten, Moore, James, Rompotis, Dimitrios, Wang, Jinxiong, Kane, Daniel, Venkatesan, Sandhya, Meier, Joachim, Pallas, Florent, Jezynski, Tomasz, Lederer, Maximilian, Boukhelef, Djelloul, Szuba, Janusz, Wrona, Krzysztof, Zhu, Jun, Bergemann, Martin, Kamil, Ebad, Kluyver, Thomas, Rosca, Robert, Spirzewski, Michał, Kuster, Markus, Hauf, Steffen, Turcato, Monica, Lomidze, David, Samartsev, Andrey, Engelke, Jan, Porro, Matteo, Maffessanti, Stefano, Hansen, Karsten, Erdinger, Florian, Fischer, Peter, Fiorini, Carlo, Castoldi, Andrea, Manghisoni, Massimo, Wunderer, Cornelia Beatrix, Fullerton, Eric E., Shpyrko, Oleg G., Gutt, Christian, Sanchez-Hanke, Cecilia, Dürr, Hermann A., Iacocca, Ezio, Nembach, Hans T., Keller, Mark W., Shaw, Justin M., Silva, Thomas J., Kukreja, Roopali, Fangohr, Hans, Eisebitt, Stefan, Kläui, Mathias, Jaouen, Nicolas, Scherz, Andreas, Bonetti, Stefano, Jal, Emmanuelle, Zhou Hagström, Nanna, Schneider, Michael, Kerber, Nico, Yaroslavtsev, Alexander, Burgos Parra, Erick, Beg, Marijan, Lang, Martin, Günther, Christian M., Seng, Boris, Kammerbauer, Fabian, Popescu, Horia, Pancaldi, Matteo, Neeraj, Kumar, Polley, Debanjan, Jangid, Rahul, Hrkac, Stjepan B., Patel, Sheena K. K., Ovcharenko, Sergei, Turenne, Diego, Ksenzov, Dmitriy, Boeglin, Christine, Pronin, Igor, Baidakova, Marina, von Korff Schmising, Clemens, Borchert, Martin, Vodungbo, Boris, Chen, Kai, Luo, Chen, Radu, Florin, Müller, Leonard, Martínez Flórez, Miriam, Philippi-Kobs, André, Riepp, Matthias, Roseker, Wojciech, Grübel, Gerhard, Carley, Robert, Schlappa, Justine, Van Kuiken, Benjamin, Gort, Rafael, Mercadier, Laurent, Agarwal, Naman, Le Guyader, Loïc, Mercurio, Giuseppe, Teichmann, Martin, Torben Delitz, Jan, Reich, Alexander, Broers, Carsten, Hickin, David, Deiter, Carsten, Moore, James, Rompotis, Dimitrios, Wang, Jinxiong, Kane, Daniel, Venkatesan, Sandhya, Meier, Joachim, Pallas, Florent, Jezynski, Tomasz, Lederer, Maximilian, Boukhelef, Djelloul, Szuba, Janusz, Wrona, Krzysztof, Zhu, Jun, Bergemann, Martin, Kamil, Ebad, Kluyver, Thomas, Rosca, Robert, Spirzewski, Michał, Kuster, Markus, Hauf, Steffen, Turcato, Monica, Lomidze, David, Samartsev, Andrey, Engelke, Jan, Porro, Matteo, Maffessanti, Stefano, Hansen, Karsten, Erdinger, Florian, Fischer, Peter, Fiorini, Carlo, Castoldi, Andrea, Manghisoni, Massimo, Wunderer, Cornelia Beatrix, Fullerton, Eric E., Shpyrko, Oleg G., Gutt, Christian, Sanchez-Hanke, Cecilia, Dürr, Hermann A., Iacocca, Ezio, Nembach, Hans T., Keller, Mark W., Shaw, Justin M., Silva, Thomas J., Kukreja, Roopali, Fangohr, Hans, Eisebitt, Stefan, Kläui, Mathias, Jaouen, Nicolas, Scherz, Andreas, Bonetti, Stefano, and Jal, Emmanuelle

Abstract

The advent of X-ray free-electron lasers (XFELs) has revolutionized fundamental science, from atomic to condensed matter physics, from chemistry to biology, giving researchers access to X-rays with unprecedented brightness, coherence, and pulse duration. All XFEL facilities built until recently provided X-ray pulses at a relatively low repetition rate, with limited data statistics. Here, we present the results from the first megahertz repetition rate X-ray scattering experiments at the Spectroscopy and Coherent Scattering (SCS) instrument of the European XFEL. We illustrate the experimental capabilities that the SCS instrument offers, resulting from the operation at MHz repetition rates and the availability of the novel DSSC 2D imaging detector. Time-resolved magnetic X-ray scattering and holographic imaging experiments in solid state samples were chosen as representative examples, providing an ideal test-bed for operation at megahertz rates. Nevertheless, our results are relevant and applicable to any other non-destructive XFEL experiments in the soft X-ray range.

109. Strain Engineering of Epitaxial Pt/Fe Spintronic Terahertz Emitter

Author

Gupta, Rahul, Bagherikorani, Ebrahim, Mottamchetty, Venkatesh, Pavelka, Martin, Jatkar, Kasturie, Dancila, Dragos, Mohammadpour-Aghdam, Karim, Faraji-Dana, Reza, Rydberg, Anders, Brucas, Rimantas, Dürr, Hermann, Svedlindh, Peter, Gupta, Rahul, Bagherikorani, Ebrahim, Mottamchetty, Venkatesh, Pavelka, Martin, Jatkar, Kasturie, Dancila, Dragos, Mohammadpour-Aghdam, Karim, Faraji-Dana, Reza, Rydberg, Anders, Brucas, Rimantas, Dürr, Hermann, and Svedlindh, Peter

Abstract

Spin-based terahertz (THz) emitters, utilizing the inverse spin Hall effect, are ultra-modern sources for the generation of THz electromagnetic radiation. To make a powerful emitter having large THz amplitude and bandwidth, fundamental understanding in terms of microscopic models is essential. This study reveals important factors to engineer the THzemission amplitude and bandwidth in epitaxial Pt/Fe emitters grown on MgO and MgAl2O4 (MAO) substrates, where the choice of the substrate plays an important role. The THz amplitude and bandwidth are affected by the induced strain in the Fe spin source layer. On the one hand, the THz electric field amplitude is found to be larger when Pt/Fe is grown on MgO even though the crystalline quality of the Fe film is superior when grown on MAO. This is because of the larger defect density, smaller electron relaxation time, and lower electrical conductivity in the THz regime when Fe is grown on MgO. On the other hand, the bandwidth is found to be larger for Pt/Fe grown on MAO and is explained by the uncoupled/coupled Lorentz oscillator models. This study provides an insightful pathway to further engineer metallic spintronic THz emitters in terms of the proper choice of substrate and microscopic properties of the emitter layers.

110. Parallel Broadband Femtosecond Reflection Spectroscopy at a Soft X-Ray Free-Electron Laser

Author

Engel, Robin Y., Miedema, Piter S., Turenne, Diego, Vaskivskyi, Igor, Brenner, Günter, Dziarzhytski, Siarhei, Kuhlmann, Marion, Schunck, Jan O., Döring, Florian, Styervoyedov, Andriy, Parkin, Stuart S.P., David, Christian, Schüßler-Langeheine, Christian, Dürr, Hermann A., and Beye, Martin

Subjects
transmission grating, lcsh:T, Atom and Molecular Physics and Optics, X-ray absorption spectroscopy, Acceleratorfysik och instrumentering, free electron laser, X-ray reflectivity, Accelerator Physics and Instrumentation, lcsh:Technology, lcsh:QC1-999, lcsh:Chemistry, intensity normalization, lcsh:Biology (General), lcsh:QD1-999, lcsh:TA1-2040, Atom- och molekylfysik och optik, lcsh:Engineering (General). Civil engineering (General), lcsh:QH301-705.5, ddc:600, lcsh:Physics
Abstract

X-ray absorption spectroscopy (XAS) and the directly linked X-ray reflectivity near absorption edges yield a wealth of specific information on the electronic structure around the resonantly addressed element. Observing the dynamic response of complex materials to optical excitations in pump&ndash, probe experiments requires high sensitivity to small changes in the spectra which in turn necessitates the brilliance of free electron laser (FEL) pulses. However, due to the fluctuating spectral content of pulses generated by self-amplified spontaneous emission (SASE), FEL experiments often struggle to reach the full sensitivity and time-resolution that FELs can in principle enable. Here, we implement a setup which solves two common challenges in this type of spectroscopy using FELs: First, we achieve a high spectral resolution by using a spectrometer downstream of the sample instead of a monochromator upstream of the sample. Thus, the full FEL bandwidth contributes to the measurement at the same time, and the FEL pulse duration is not elongated by a monochromator. Second, the FEL beam is divided into identical copies by a transmission grating beam splitter so that two spectra from separate spots on the sample (or from the sample and known reference) can be recorded in-parallel with the same spectrometer, enabling a spectrally resolved intensity normalization of pulse fluctuations in pump&ndash, probe scenarios. We analyze the capabilities of this setup around the oxygen K- and nickel L-edges recorded with third harmonic radiation of the free electron laser in Hamburg (FLASH), demonstrating the capability for pump&ndash, probe measurements with sensitivity to reflectivity changes on the per mill level.

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112. Nonequilibrium electron and lattice dynamics of strongly correlated Bi2Sr2CaCu2O8+δ single crystals.

Author

Konstantinova, Tatiana, Rameau, Jonathan D., Reid, Alexander H., Abdurazakov, Omadillo, Lijun Wu, Renkai Li, Xiaozhe Shen, Genda Gu, Yuan Huang, Rettig, Laurenz, Avigo, Isabella, Ligges, Manuel, Freericks, James K., Kemper, Alexander F., Dürr, Hermann A., Bovensiepen, Uwe, Johnson, Peter D., Xijie Wang, and Yimei Zhu

Subjects
*SUPERCONDUCTORS, *ELECTRON-phonon interactions, *CUPRATES, *PHONONS, *ENERGY dissipation
Abstract

The article presents a study on Bi2Sr2CaCu2O8+δ superconductors which depicts nonequilibrium electron-phonon interactions in the cuprates beyond the N-temperature model. The study highlights specific phonon branches involved in the nonequilibrium heat dissipation from the high-energy copper-oxygen bond stretching "hot" phonons to the lowest-energy acoustic phonons with correlated atomic motion.

Published
2018
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117. Femtosecond single-shot imaging of nanoscale ferromagnetic order in Co/Pd multilayers using resonant x-ray holography.

Author

Wang T, Zhu D, Wu B, Graves C, Schaffert S, Rander T, Müller L, Vodungbo B, Baumier C, Bernstein DP, Bräuer B, Cros V, de Jong S, Delaunay R, Fognini A, Kukreja R, Lee S, López-Flores V, Mohanty J, Pfau B, Popescu H, Sacchi M, Sardinha AB, Sirotti F, Zeitoun P, Messerschmidt M, Turner JJ, Schlotter WF, Hellwig O, Mattana R, Jaouen N, Fortuna F, Acremann Y, Gutt C, Dürr HA, Beaurepaire E, Boeglin C, Eisebitt S, Grübel G, Lüning J, Stöhr J, and Scherz AO

Abstract

We present the first single-shot images of ferromagnetic, nanoscale spin order taken with femtosecond x-ray pulses. X-ray-induced electron and spin dynamics can be outrun with pulses shorter than 80 fs in the investigated fluence regime, and no permanent aftereffects in the samples are observed below a fluence of 25 mJ/cm(2). Employing resonant spatially muliplexed x-ray holography results in a low imaging threshold of 5 mJ/cm(2). Our results open new ways to combine ultrafast laser spectroscopy with sequential snapshot imaging on a single sample, generating a movie of excited state dynamics.

Published
2012
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118. Hot-electron-driven enhancement of spin-lattice coupling in Gd and Tb 4f ferromagnets observed by femtosecond x-ray magnetic circular dichroism.

Author

Wietstruk M, Melnikov A, Stamm C, Kachel T, Pontius N, Sultan M, Gahl C, Weinelt M, Dürr HA, and Bovensiepen U

Abstract

Femtosecond x-ray magnetic circular dichroism was used to study the time-dependent magnetic moment of 4f electrons in the ferromagnets Gd and Tb, which are known for their different spin-lattice coupling. We observe a two-step demagnetization with an ultrafast demagnetization time of 750 fs identical for both systems and slower times which differ sizeably with 40 ps for Gd and 8 ps for Tb. We conclude that spin-lattice coupling in the electronically excited state is enhanced up to 50 times compared to equilibrium.

Published
2011
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