Magnetic vortices are characterized by the chirality of the curl of the magnetization and the polarity of the vortex core. This leads to four possible stable magnetization configurations that can be utilized in a multi-bit memory cell. Ultrafast control of vortex core polarity has been shown using both alternating and pulsed magnetic fields and currents. Here we demonstrate ultrafast switching of vortex chirality using nanosecond field pulses by imaging the process with full-field x-ray transmission microscopy. The dynamic reversal process is controlled by far-from-equilibrium gyrotropic precession of the vortex core and the reversal is achieved at significantly reduced field amplitudes when compared to quasi-static switching. We further show that both the field pulse amplitude and duration required for efficient chirality reversal can be controlled by selection of the disk geometry.
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