Dynamics of magnetic vortices and antivortices studied by ferromagnetic absorption spectroscopy and transmission x-ray microscopy

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Magnetic singularities in micron-sized ferromagnetic elements are promising for innovative magnetic data storage and serve as an ideal model for studying magnetization dynamics. This work focuses on the dynamics of magnetic vortices and antivortices at picosecond and nanosecond timescales. High-frequency alternating fields and spin-polarized currents manipulate the magnetic states of these structures. The research explores rotational excitation through time-resolved magnetic transmission x-ray microscopy, micromagnetic simulations, and analytical calculations. Notably, magnetic antivortices exhibit an asymmetric response to field and current excitation, which can be attributed to their domains' negative winding number. Additionally, the dynamics of magnetic vortices are examined in the frequency domain using ferromagnetic absorption spectroscopy, revealing deviations from previously assumed linear dynamics. These deviations are explained by a nonparabolic confining potential and a critical maximum velocity of vortex motion. The absorption spectra are significantly affected by the continuous reversal of vortex-core polarization at high excitation amplitudes. The insights gained into vortex dynamics are essential for the effective application of vortices in data storage technologies.