@article{KwamenRoessleReinhardtetal.2017,
  author    = {Kwamen, C. and R{\"o}ssle, Matthias and Reinhardt, M. and Leitenberger, Wolfram and Zamponi, Flavio and Alexe, Marin and Bargheer, Matias},
  title     = {Simultaneous dynamic characterization of charge and structural motion during ferroelectric switching},
  series = {Physical review : B, Condensed matter and materials physics},
  volume    = {96},
  journal   = {Physical review : B, Condensed matter and materials physics},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {2469-9950},
  doi       = {10.1103/PhysRevB.96.134105},
  pages     = {6},
  year      = {2017},
  abstract  = {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.},
  language  = {en}
}
@article{SanderKocKwamenetal.2016,
  author    = {Sander, Mathias and Koc, A. and Kwamen, C. T. and Michaels, H. and Reppert, Alexander von and Pudell, Jan-Etienne and Zamponi, Flavio and Bargheer, Matias and Sellmann, J. and Schwarzkopf, J. and Gaal, P.},
  title     = {Characterization of an ultrafast Bragg-Switch for shortening hard x-ray pulses},
  series = {Journal of applied physics},
  volume    = {120},
  journal   = {Journal of applied physics},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0021-8979},
  doi       = {10.1063/1.4967835},
  pages     = {7},
  year      = {2016},
  abstract  = {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.},
  language  = {en}
}
@article{IurchukSchickBranetal.2016,
  author    = {Iurchuk, V. and Schick, D. and Bran, J. and Colson, D. and Forget, A. and Halley, D. and Koc, Azize and Reinhardt, Mathias and Kwamen, C. and Morley, N. A. and Bargheer, Matias and Viret, M. and Gumeniuk, R. and Schmerber, G. and Doudin, B. and Kundys, B.},
  title     = {Optical Writing of Magnetic Properties by Remanent Photostriction},
  series = {Physical review letters},
  volume    = {117},
  journal   = {Physical review letters},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {0031-9007},
  doi       = {10.1103/PhysRevLett.117.107403},
  pages     = {5},
  year      = {2016},
  abstract  = {We present an optically induced remanent photostriction in BiFeO3, resulting from the photovoltaic effect, which is used to modify the ferromagnetism of Ni film in a hybrid BiFeO3/Ni structure. The 75\% change in coercivity in the Ni film is achieved via optical and nonvolatile control. This photoferromagnetic effect can be reversed by static or ac electric depolarization of BiFeO3. Hence, the strain dependent changes in magnetic properties are written optically, and erased electrically. Light-mediated straintronics is therefore a possible approach for low-power multistate control of magnetic elements relevant for memory and spintronic applications.},
  language  = {en}
}