An atomic‐scale vector network analyzer

Electronic devices have been ever‐shrinking toward atomic dimensions and have reached operation frequencies in the GHz range, thereby outperforming most conventional test equipment, such as vector network analyzers (VNA). Here the capabilities of a VNA on the atomic scale in a scanning tunneling microscope are implemented. Nonlinearities present in the voltage‐current characteristic of atoms and nanostructures for phase‐resolved microwave spectroscopy with unprecedented spatial resolution at GHz frequencies are exploited. The amplitude and phase response up to 9.3 GHz is determined, which permits accurate de‐embedding of the transmission line and application of distortion‐corrected waveforms in the tunnel junction itself. This enables quantitative characterization of the complex‐valued admittance of individual magnetic iron atoms which show a lowpass response with a magnetic‐field‐tunable cutoff frequency.Horizon 2020 Framework Programm

Burst-mode manipulation of magnonic vortex crystals

The manipulation of polarization states in 4 × 4 vortex crystals using sinusoidal magnetic field bursts isinvestigated by means of a broadband ferromagnetic-resonance setup. Magnetic field excitation with the properamplitude and frequency allows tuning different polarization states, which are observed in the measured absorptionspectra. The variation of the sinusoidal burst width consecutively identifies the time scale of the underlyingprocess. A memorylike polarization state writing process is demonstrated on the submicrosecond time scale

Burst-mode manipulation of magnonic vortex crystals

The manipulation of polarization states in 4 × 4 vortex crystals using sinusoidal magnetic field bursts isinvestigated by means of a broadband ferromagnetic-resonance setup. Magnetic field excitation with the properamplitude and frequency allows tuning different polarization states, which are observed in the measured absorptionspectra. The variation of the sinusoidal burst width consecutively identifies the time scale of the underlyingprocess. A memorylike polarization state writing process is demonstrated on the submicrosecond time scale

Gyrational modes of benzenelike magnetic vortex molecules

With scanning transmission x-ray microscopy we study six magnetostatically coupled vortices arranged in a ring that resembles a benzene molecule. Each vortex is contained in a ferromagnetic microdisk. When exciting one vortex of the ring molecule with an alternating magnetic high-frequency field, all six vortices perform gyrations around the equilibrium center positions in their disks. In a rigid particle model, we derive the dispersion relation for these modes. In contrast to carbon atoms, magnetic vortices have a core polarization that strongly influences the intervortex coupling. We make use of this state parameter to reprogram the dispersion relation of the vortex molecule experimentally by tuning a homogeneous and an alternating polarization pattern. In analogy to the benzene molecule, we observe motions that can be understood in terms of normal modes that are largely determined by the symmetry of the system

Band structure engineering of two-dimensional magnonic vortex crystals

Magnonic vortex crystals are studied via scanning transmission x-raymicroscopy and ferromagnetic-resonance spectroscopy. We investigate a two-dimensional vortex crystal by imprinting waves with tunable wave vectors. The dispersion relation ω(k) is determined via ferromagnetic-resonance spectroscopy with a tunable frequency and wave vector for two vortex core polarization patterns that are adjusted by self-organized state formation prior to the measurement. We demonstrate that the band structure of the crystal is reprogrammed by tuning the vortexpolarizations

Band Structure Engineering of Two-Dimensional Magnonic Vortex Crystals

Magnonic vortex crystals are studied via scanning transmission x-raymicroscopy and ferromagnetic-resonance spectroscopy. We investigate a two-dimensional vortex crystal by imprinting waves with tunable wave vectors. The dispersion relation ω(k) is determined via ferromagnetic-resonance spectroscopy with a tunable frequency and wave vector for two vortex core polarization patterns that are adjusted by self-organized state formation prior to the measurement. We demonstrate that the band structure of the crystal is reprogrammed by tuning the vortexpolarizations

Gyrational modes of benzenelike magnetic vortex molecules

With scanning transmission x-ray microscopy we study six magnetostatically coupled vortices arranged in a ring that resembles a benzene molecule. Each vortex is contained in a ferromagnetic microdisk. When exciting one vortex of the ring molecule with an alternating magnetic high-frequency field, all six vortices perform gyrations around the equilibrium center positions in their disks. In a rigid particle model, we derive the dispersion relation for these modes. In contrast to carbon atoms, magnetic vortices have a core polarization that strongly influences the intervortex coupling. We make use of this state parameter to reprogram the dispersion relation of the vortex molecule experimentally by tuning a homogeneous and an alternating polarization pattern. In analogy to the benzene molecule, we observe motions that can be understood in terms of normal modes that are largely determined by the symmetry of the system

Two-body problem of core-region coupled magnetic vortex stacks

The dynamics of all four combinations of possible polarity and circularity states in a stack of two vorticesis investigated by time-resolved scanning transmission x-ray microscopy. The vortex stacks are excited byunidirectional magnetic fields leading to a collective oscillation. Four different modes are observed that dependon the relative polarizations and circularities of the stacks. They are excited to a driven oscillation. We observe arepulsive and attractive interaction of the vortex cores depending on their relative polarizations. The nonlinearityof this core interaction results in different trajectories that describe a two-body problem

Spin-wave interference in magnetic vortex stacks

Spin waves are promising candidates as a building block for future magnonic devices. The authors present a combined numerical and experimental study of spin-wave interferences in stacks of magnetic vortices that are efficient spin-wave emitters in the nanometre regime