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  - Sander, Mathias
A1  - Koc, A.
A1  - Kwamen, C. T.
A1  - Michaels, H.
A1  - Reppert, Alexander von
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  - Iurchuk, V.
A1  - Schick, D.
A1  - Bran, J.
A1  - Colson, D.
A1  - Forget, A.
A1  - Halley, D.
A1  - Koc, Azize
A1  - Reinhardt, Mathias
A1  - Kwamen, C.
A1  - Morley, N. A.
A1  - Bargheer, Matias
A1  - Viret, M.
A1  - Gumeniuk, R.
A1  - Schmerber, G.
A1  - Doudin, B.
A1  - Kundys, B.
T1  - Optical Writing of Magnetic Properties by Remanent Photostriction
JF  - Physical review letters
N2  - 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.
Y1  - 2016
U6  - https://doi.org/10.1103/PhysRevLett.117.107403
SN  - 0031-9007
SN  - 1079-7114
VL  - 117
PB  - American Physical Society
CY  - College Park
ER  -