A5067317596- Magnetic properties of thin films
- Physics of Superconductivity and Magnetism
- Crystallography and Radiation Phenomena
- Characterization and Applications of Magnetic Nanoparticles
- Magnetic Properties and Applications
- Quantum and electron transport phenomena
- Advanced X-ray Imaging Techniques
- Advanced Electron Microscopy Techniques and Applications
- Mechanical and Optical Resonators
- Laser-Matter Interactions and Applications
- Spectroscopy and Quantum Chemical Studies
- Topological Materials and Phenomena
- Advanced Chemical Physics Studies
- Quantum optics and atomic interactions
- Theoretical and Computational Physics
- ZnO doping and properties
- Advanced Condensed Matter Physics
- Magneto-Optical Properties and Applications
- Anodic Oxide Films and Nanostructures
- Terahertz technology and applications
- Multiferroics and related materials
- Magnetic Properties of Alloys
- Fluid Dynamics and Turbulent Flows
- Advanced Data Storage Technologies
- Heusler alloys: electronic and magnetic properties
Deutsches Elektronen-Synchrotron DESY
2015-2024
Max Planck Institute for the Structure and Dynamics of Matter
2014-2024
Hamburg Centre for Ultrafast Imaging
2014-2024
Universität Hamburg
2007-2022
Helmut Schmidt University
2022
University of New York in Prague
2022
Charles University
2022
Imperial College London
2022
European X-Ray Free-Electron Laser
2022
GSI Helmholtz Centre for Heavy Ion Research
2022
The stochastic field-driven depinning of a domain wall pinned at notch in magnetic nanowire is directly observed using x-ray microscopy with high lateral resolution down to 15 nm. depinning-field distribution Ni80Fe20 nanowires considerably depends on the wire width and depth. difference multiplicity domain-wall types generated vicinity responsible for dependence nature field Thus random process controllable by an appropriate design nanowire.
Time-resolved x-ray microscopy is used to image the influence of alternating high-density currents on magnetization dynamics ferromagnetic vortices. Spin-torque-induced vortex gyration observed in micrometer-sized permalloy squares. The phases structures with different chirality are compared an analytical model and micromagnetic simulations, considering both spin-polarized current's Oersted field. In our case driving force due spin-transfer torque about 70% total excitation while remainder...
A wide variety of coupled harmonic oscillators exist in nature1. Coupling between different allows for the possibility mutual energy transfer them2-4 and information-signal propagation5,6. Low-energy input signals their transport with low-energy dissipation are key technical factors design information processing devices7. Here, utilizing concept oscillators, we experimentally demonstrated a robust new mechanism spatially separated dipolar-coupled magnetic disks - stimulated vortex gyration....
Group velocity control is demonstrated for x-ray photons of 14.4 keV energy via a direct measurement the temporal delay imposed on spectrally narrow pulses. Subluminal light propagation achieved by inducing steep positive linear dispersion in optical response Fe57 Mössbauer nuclei embedded thin film planar cavity. The detection pulse enabled generating frequency-tunable pulses from broadband pulsed synchrotron radiation. Our theoretical model good agreement with experimental data.Received 29...
Here, we use x-rays to create and probe quantum coherence in the photoionized amino acid glycine. The outgoing photoelectron leaves behind cation a coherent superposition of mechanical eigenstates. Delayed x-ray pulses track induced through resonant absorption that induces Auger decay by emission from sequential double photoionization. Sinusoidal temporal modulation detected signal at early times (0 25 fs) is observed both measurements. Advanced ab initio many-electron simulations allow us...
Optical quantum memories are key elements in modern technologies to reliably store and retrieve information. At present, they conceptually limited the optical wavelength regime. Recent advancements x-ray optics render an extension of memory protocols ultrashort wavelengths possible, thereby establishing photonics at energies. Here, we introduce protocol that utilizes mechanically driven nuclear resonant
We employed time- and space-resolved full-field magnetic transmission soft x-ray microscopy to observe vortex-core gyrations in a pair of dipolar-coupled vortex-state Permalloy (Ni80Fe20) disks. The 70 ps temporal 20 nm spatial resolution the microscope enabled us simultaneously measure vortex both disks resolve phases amplitudes positions. observed their correlation for specific configuration. This work provides robust direct method studying oscillators.
Current-induced domain-wall dynamics is investigated via high-resolution soft x-ray transmission microscopy by a stroboscopic pump-and-probe measurement scheme at temporal resolution of 200 ps. A $180\ifmmode^\circ\else\textdegree\fi{}$ domain wall in restoring potential permalloy microstructure displaced from its equilibrium position nanosecond current pulses leading to oscillations with velocities up 325 m/s. The motion the described an analytical model rigid nonharmonic allowing one...
A dependence of current-induced domain-wall motion in nanowires on the temporal shape current pulses is observed. The results show that wall amplified for alterations a time scale smaller than intrinsic domain which few nanoseconds permalloy. This effect arises from an additional force by spin-transfer torque due to fast changing and improves efficiency motion. observations provide understanding efficient with nanosecond pulses.
We demonstrate by micromagnetic simulations that magnetic antivortices are potential candidates for fast nonvolatile data-storage elements. These storage elements excited simultaneously alternating spin-polarized currents and their accompanying Oersted fields. Depending on the antivortex-core polarization p orientation of in-plane magnetization c around core, superposition current field leads to either a suppression gyration (logical "zero") or an increased amplitude "one"). Above excitation...
We study field- and current-induced domain-wall motion in permalloy nanowires containing a square-shaped magnetically softened region. Implantation of chromium ions is used to induce pinning sites via local reduction the saturation magnetization. Micromagnetic simulations, magnetic transmission soft x-ray microscopy, electrical measurements are employed characterize potential which significantly differs for transverse vortex walls. Reliable depinning from so-called spot by single current...
We demonstrate the feasibility of investigating periodically driven magnetization dynamics in a scanning electron microscope with polarization analysis based on spin-polarized low-energy diffraction. With present setup, analyzing time structure scattering events, we obtain temporal resolution 700 ps, which is demonstrated by means imaging field-driven 100 MHz gyration vortex soft-magnetic FeCoSiB square. Owing to efficient intrinsic timing scheme, high-quality movies, giving two components...
In ferromagnetic nanostructures domain walls as emergent entities separate uniformly magnetized regions. They are describable quasi particles and can be controlled by magnetic fields or spin-polarized currents. Below critical driving forces rigid conserving their spin structure. Like other internal excitations influence the wall dynamics above a velocity known Walker breakdown. This complex nonlinear motion has not been observed directly. Here we present direct time-resolved x-ray microscopy...
Here we present the results of a classical ghost imaging experiment accomplished at an XUV free-electron laser (FEL). To perform such FEL source each x-ray pulse was transmitted through moving diffuser, which created noncorrelated speckled beam. This beam then split in two identical branches by introducing splitter form transmission grating. In one these sample positioned. We demonstrate possibility image formation, double bar our case, that has never interacted with sample. With this extend...
A collective nuclear state is coherently controlled via a solid’s quasi-particle with zeptosecond precision.
We present point-contact Andreev reflection (PCAR) spectroscopy on Permalloy (Ni80Fe20) and the half-metallic Heusler alloy Ni2MnIn. The thin films are deposited Si, Ni2MnIn Si as well in situ cleaved (110) surfaces of InAs. A highly conductive layer under ferromagnetic film almost eliminates a series resistance thus facilitates determination spin polarization from differential conductance curves. obtain 35%. depends substrate, presumably due to growth different crystal structures. It is...
The generation of short spin current pulses is the basis for fast spintronic devices. In thin bilayer systems consisting a nonmagnetic metal and ferromagnet, pure induced by precessing magnetization into layer pumping. This effect has been experimentally demonstrated at ferromagnetic resonance GHz frequencies. Here, it theoretically shown that transient dynamics efficiently generates exhibit two contributions. An effective coherent found far above up to THz frequencies although dynamic...
Domain walls in curved Permalloy (Ni80Fe20) nanowires are depinned by nanosecond current pulses and magnetic fields. A significant dependence of the depinning probability on pulse length is observed. We measure an oscillatory with a characteristic frequency 270 MHz. The quality used for crucial efficient domain-wall depinning. By sputtering heated substrates we able to considerably decrease specific resistance that found directly correspond field domain wall.
We probe the spin dynamics in a thin magnetic film at ferromagnetic resonance by nuclear resonant scattering of synchrotron radiation 14.4 keV ^{57}Fe. The precession magnetization leads to an apparent reduction hyperfine field acting ^{57}Fe nuclei. is described stochastic relaxation model adapted theory Smit and Beljers decay excited state. From fits measured data, shape cone spins determined. Our results open new perspective determine layered structures with very high depth resolution...
Magnetoelectronic multilayer devices are widely used in today's information and sensor technology. Their functionality, however, is limited by the inherent properties of magnetic exchange or dipolar coupling which constrain possible spin configurations to collinear perpendicular alignments adjacent layers. Here, a deposition procedure introduced that allows for new class layered materials complex structures can be accurately designed result multitude precisely adjustable spintronic...
Abstract Magnetization dynamics can be coherently controlled by THz laser excitation, which applied in ultrafast magnetization control and switching. Here, transient are calculated for excitation with magnetic field pulses. We use the ansatz of Smit Beljers, to formulate dynamic properties via partial derivatives samples free energy density extend it solve Landau-Lifshitz-equation obtain transients magnetization. The model is used determine response multi- single-cycle Control trajectory...
Abstract Wave packet interferometry provides benchmark information on light-induced electronic quantum states by monitoring their relative amplitudes and phases during coherent excitation, propagation, decay. The phase control of soft x-ray pulse replicas the single-digit attosecond timescale achieved in our experiments makes this method a powerful tool to probe ultrafast phenomena such as excitation Auger shake-up with sub-cycle precision. In contribution we present first results obtained...