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Spin wave emission and propagation in magnonic waveguides represent a highly promising alternative for beyond-CMOS computing. It is therefore all the more important to fully understand the underlying physics of the emission process. Here, we use time-resolved scanning transmission x-ray microscopy to directly image the formation process of the globally excited local emission of spin waves in a permalloy waveguide at the nanoscale. Thereby, we observe spin wave emission from the corner of the waveguide as well as from a local oscillation of a domain-wall-like structure within the waveguide. Additionally, an isofrequency contour analysis is used to fully explain the origin of quasicylindrical spin wave excitation from the corner and its concurrent nonreflection and nonrefraction at the domain interface. This study is complemented by micromagnetic simulations which perfectly fit the experimental findings. Thus, we clarify the fundamental question of the emission mechanisms in magnonic waveguides which lay the basis for future magnonic operations.

Scanning transmission x-ray microscopy has been used to image electric currents in superconducting films at temperatures down to 20 K. We detect significant deviations from a regular current path driven by macroscopic geometrical constraints. The magnetic stray field of supercurrents in a thin YBaCuO film is mapped into a soft-magnetic coating of permalloy. The so-created local magnetization of the ferromagnetic film can be detected by dichroic absorption of polarized x rays. To enable high-quality measurements in transmission geometry, the whole heterostructure of ferromagnet, superconductor, and single-crystalline substrate has been thinned to an overall thickness of less than 1 \textmu{}m. With this technique, local supercurrents can be analyzed in a wide range of temperatures and magnetic fields. The less than 100 nm spatial resolution of the magnetic signal together with simultaneously obtained nanostructural data allow the correlation of local supercurrents with the micro- and nanostructure of the superconducting film.

Vortex structures in confined geometries are currently under close scrutiny due to their unique properties associated with their spatial confinement and the non-uniform distribution of the magnetization. The magnetic vortex is characterized by two boolean topological quantities: circulation (clockwise or counterclockwise c = ± 1) of the in-plane magnetization and polarity (up or down, p = ± 1) of the vortex core. These four degenerate states are quite stable and can accelerate the development of more compact and high performance magnetic memory devices. Thus an understanding of their dynamical behavior and a way to electrically detect these states is a major requirement for their development. Progress can be achieved by combining theoretical calculations, micromagnetic simulations and experimental approaches. The phenomenon of spin transfer torque is exploited to excite the lowest frequency (gyro) mode of the vortex core confined in a submicron magnetic (Permalloy - Ni81Fe19) element. The gyrotropic motion of the vortex core leads to a periodic change in the magnetization and hence its resistance: due to the anisotropic magnetoresistance (AMR) effect. This periodic change in resistance combines with the excitation current and generates a periodic homodyne voltage signal. An external static magnetic field is applied to break the symmetry and to rectify the homodyne voltage signal which we measure in a nanovoltmeter. It is found that the sign of the rectified AMR signal depends upon the handedness (cp) of the vortex structure. Micromagnetic simulations provide better understanding and are in good agreement with our experimental results. Additionally, vortex dynamics in these samples is investigated in a Scanning Transmission X-ray Microscope (STXM) with a temporal (< 100 ps) and spatial (~ 30 nm) resolution which allows us to verify the resonance frequency of the magnetic element as well as the power range to excite the vortex core. The AMR based technique thus can be used to detect the circulation and the polarity of the vortex state electrically and could open a route to implement magnetic vortex elements in memory and storage hierarchies. The phenomenon of Spin Motive Force (SMF) has also been studied by micromagnetic simulations. It is found that, in a particular configuration, the SMF signal shows a phase difference of 180 degrees for two polarities of the vortex core, when the voltage probe contacts are located parallel to the excitation rf field direction. No phase shift is observed in the perpendicular case. In addition, a 180 degree phase difference is observed for different circulations of the vortex structure. Therefore, this could also be a possible way to determine polarity and circulation of the magnetic vortex by carefully examining the phase relation of the SMF generated voltage signals. An attempt has also been made to measure the SMF experimentally. However, due to the small expected signal unambiguous detection of SMF was not successful so far.

The magnetic vortex structure, an important ground state configuration in micron and sub-micron sized ferromagnetic thin film platelets, is characterized by a curling in-plane magnetization and, in the center, a minuscule region with out-of-plane magnetization, the vortex core, which points either up or down. It has already been demonstrated that the vortex core polarity can be reversed with external AC magnetic fields, frequency-tuned to the (sub-GHz) gyrotropic eigenmode or to (multi-GHz) azimuthal spin wave modes, where reversal times in the sub-ns regime can be realized. This fast vortex core switching may also be of technological interest as the vortex core polarity can be regarded as one data bit. Here we experimentally demonstrate that unidirectional vortex core reversal by excitation with sub-100 ps long orthogonal monopolar magnetic pulse sequences is possible in a wide range of pulse lengths and amplitudes. The application of such short digital pulses is the favourable excitation scheme for technological applications. Measured phase diagrams of this unidirectional, spin wave mediated vortex core reversal are in good qualitative agreement with phase diagrams obtained from micromagnetic simulations. The time dependence of the reversal process, observed by time-resolved scanning transmission X-ray microscopy indicates a switching time of 100 ps and fits well with our simulations. The origin of the asymmetric response to clockwise and counter clockwise excitation which is a prerequisite for reliable unidirectional switching is discussed, based on the gyromode - spin wave coupling.

The magnetic flux distribution arising from a high-${T}_{c}$ superconductor is detected and visualized using polarized x rays. Therefore, we introduce a sensor layer, namely, an amorphous, soft-magnetic ${\mathrm{Co}}_{40}{\mathrm{Fe}}_{40}{\mathrm{B}}_{20}$ cover layer, providing a large x-ray magnetic circular dichroism (XMCD). Temperature-dependent XMCD spectroscopy on the magnetic layer has been performed. Exploiting the temperature dependence of the critical current density of the superconductor we find a quantitative correlation between the XMCD signal and the in-plane stray field of the superconductor. Magneto-optical Kerr effect experiments on the sensor layer can simulate the stray field of the superconductor and hence verify the correlation. We show that the XMCD contrast in the sensor layer corresponds to the in-plane magnetic flux distribution of the superconductor and can hence be used to image magnetic structures in superconductors.

The motion of domain walls is influenced by their internal structure and their structural changes during motion. The macroscopic motion is well understood but the internal dynamics during motion have not been experimentally studied in detail. We study vortex domain walls excited by nanosecond long magnetic field pulses in a pinning potential and above the pinning threshold. The dynamic response is imaged by transmission x-ray microscopy and the structural changes are analyzed. From the directly observed inertial behavior of the wall the domain-wall mass equivalent is estimated. During motion, oscillations of both the vortex core around the center of the domain wall and the domain-wall width are observed. The wall shows a fully elastic behavior by compression and overexpansion when being pushed by the field.

Complexity created by periodic arrangement of well-understood building blocks plays an important role in biochemistry, photonics, engineering and nanoelectrics. The periodic arrangement of atoms or molecules as basis determines the physical properties of crystals. With the flexibility of nanometer precise electron-beam lithography here magnetic interactions are engineered yielding two-dimensional magnonic crystals that benefit from the magnetic vortex core as crystal basis. Using scanning transmission X-ray microscopy at the MAXYMUS beamline at BESSY II in Berlin, Germany the magnonic crystal dynamics are imaged with time resolution in the sub-nanosecond regime and simultaneous spatial resolution on the nanometer scale. Self-organized vortex core state formation by adiabatic reduction of a high frequency magnetic field excitation is observed. The emerging polarization states are shown to depend on the frequency of excitation and the strength of the dipolar interaction between the elements. In spite of the complexity of the investigated system, global order caused by local interactions creates polarization states with a high degree of symmetry. An analytical dipole model and numerically solved coupled equations of motion are adopted to analytically describe the experimental results. The emerging states can be predicted by a fundamental stability criterion based on the excitability of eigenmodes in the crystal. Further experiments with ferromagnetic absorption spectroscopy are carried out that give insight into the characteristic frequencies of the vortex dynamics that are crucially influenced by the self-organized state formation. This is emphasized with experiments on benzene-like magnetic vortex molecules whose motions show strong similarities to the vibrational modes of the actual benzene molecule (C6H6). The symmetry of both systems determines the motions of the oscillators, i.e., the carbon atoms or the magnetic vortices. This allows to simplify the derivation of the fundamentally different dispersion relations depending on the previously tuned polarization state. The experiments confirm the calculations and prove that the magnetic vortex molecule features a reprogrammable band structure or dispersion relation. Consequently, this work allows further research studies to tailor the characteristic properties of various magnetic vortex arrangements by tuning the polarization state. Consequently, this work allows further research studies to tailor the characteristic properties of various magnetic vortex arrangements by tuning the polarization state. Das Zusammenspiel einer Vielzahl gleichartiger, gut verstandener Bausteine spielt eine entscheidende Rolle in vielen komplexen Systemen verschiedenster wissenschaftlicher Disziplinen wie Biochemie, Photonik, Ingenieurswissenschaften oder Nanoelektronik. Zum Beispiel bestimmen periodische Anordnungen von Atomen oder Molekulen die physikalischen Eigenschaften von Kristallen. In dieser Arbeit werden magnetisch wechselwirkende Wirbel, sogenannte magnetische Vortizes, zu magnonischen Kristallen angeordnet. Die verwendete Elektronenstrahl-Lithographie erlaubt es, die Vortizes mit Nanometer-Prazision herzustellen und als Basis auf einer regelmassigen Kristallstruktur zu platzieren. Mittels zeitaufgeloster Rontgenmikroskopie am MAXYMUS Mikroskop (BESSY II Synchrotron, Helmholtz-Zentrum Berlin) ist es moglich, die dynamischen Prozesse mit einer Zeitauflosung von unter einer Nanosekunde und gleichzeitiger ortlicher Auflosung auf der Nanometer-Skala abzubilden. In den Experimenten wird ein hochfrequentes magnetisches Anregungsfeld adiabatisch reduziert. Dies fuhrt zu einer selbstorganisierten Einstellung der Polarisationen der Vortizes im Kristall. Trotz der Komplexitat der untersuchten Systeme erzeugen die lokalen Interaktionen eine globale Ordnung in Form von hochsymmetrischen Polarisationszustanden. Diese hangen von der Anregungsfrequenz und der Starke der hauptsachlich dipolaren magnetischen Wechselwirkung der Vortizes ab. Zur Beschreibung der experimentellen Ergebnisse wird ein analytisches Model entwickelt und numerisch geloste Bewegungsgleichungen werden untersucht. Die selbstorganisiert eingestellten Polarisationszustande konnen daraufhin mit einem elementaren Stabilitatskriterium erklart werden, das auf der Anregbarkeit von Eigenmoden im Kristall basiert. Weitere Messungen mit ferromagnetischer Absorptionsspektroskopie erlauben es, die deutlichen Einflusse der selbstorganisierten Zustandseinstellung auf die charakteristischen Frequenzen der Vortex-Bewegungen zu studieren. Diese Einflusse werden weiter in Experimenten an ringartigen Anordnungen von Vortizes, die starke Ahnlichkeit zum Molekul Benzol (C6H6) haben, untersucht. Bei beiden Systemen bestimmt die Symmetrie die Bewegung der Oszillatoren, das heist der Kohlenstoffatome beziehungsweise der magnetischen Vortizes. Dies erlaubt es auf vereinfachte Weise in einem analytischen Dipol-Model die Dispersionsrelation des Vortex-Molekuls herzuleiten, die stark vom vorherrschenden Polarisationszustand abhangt. In den Experimenten wird die Polarisationsabhangigkeit bestatigt und somit gezeigt, dass das magnetische Vortex-Molekul eine einstellbare Bandstruktur beziehungsweise Dispersionsrelation aufweist. Infolgedessen erlaubt es diese Arbeit weiterfuhrenden Studien die charakteristischen Eigenschaften vielfaltiger Anordnungen magnetischer Vortizes gezielt zu manipulieren und maszuschneidern.

We investigate the switching criteria of magnetic vortices in micron-sized Permalloy squares. The vortices are excited by high frequency magnetic fields. Continuous core reversal is demonstrated for a wide range of frequencies and amplitudes of excitation by ferromagnetic absorption spectroscopy and for selected frequencies and amplitudes with time-resolved scanning x-ray microscopy. The boundary of this switching regime is derived from the Thiele equation when a critical velocity of ${v}_{\mathrm{crit}}\ensuremath{\approx}250\phantom{\rule{0.222222em}{0ex}}{\mathrm{ms}}^{\ensuremath{-}1}$ is considered.

Spin-wave-mediated vortex core reversal is investigated using x-ray magnetic circular dichroism in a time-resolved scanning transmission x-ray microscope in combination with micromagnetic simulations. The evolution of magnetization dynamics in Permalloy disks is imaged after excitation with one-period rotating rf-field bursts. Selective unidirectional switching of the vortex polarity is achieved due to different switching thresholds for clockwise and counterclockwise excitations. A lower limit of about 200 ps for the unidirectional switching time after the onset of a one-period burst is found for the geometry of our disks ($1.6\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{m}$ in diameter and 50 nm in thickness).

Magnetic vortices in permalloy squares are resonantly excited by alternating magnetic fields. By static external magnetic fields their equilibrium positions and trajectories are shifted. For gyrations far away from the center of the squares strongly elongated shapes of the resonant trajectories are observed by time-resolving x-ray microscopy. Within a simple analytical model which includes isotropic and anisotropic deviations from a parabolic potential elliptical trajectories are calculated. The directions of these ellipses coincide with the experimental observations. The experimental trajectories are also compared with micromagnetic simulations.

The electronic structure of aqueous NH{sub 3} and ND{sub 3} has been investigated using resonant inelastic soft x-ray scattering. Spectral features of different processes involving nuclear dynamics in the core-excited state can be identified. When exciting into the lowest core-excited state, we find a strong isotope effect and clear evidence for ultrafast proton dynamics. Furthermore, a strong vibronic coupling is observed and, in the case of aqueous NH{sub 3}, a vibrational fine structure can be resolved.

Resonant inelastic x-ray scattering (RIXS) with soft x-rays is uniquely suited to study the elec-tronic structure of a variety of materials, but is currently limited by low (fluorescence yield) count rates. This limitation is overcome with a new high-transmission spectrometer that allows to measure soft x-ray RIXS"maps." The S L2,3 RIXS map of CdS is discussed and compared with density functional calculations. The map allows the extraction of decay channel-specific"absorp-tion spectra," giving detailed insight into the wave functions of occupied and unoccupied elec-tronic states.