  It was demonstrated recently that on ultrashort time scales magnetization
dynamics does not only exhibit precession but also nutation. Here, we
investigate how nutation can contribute to spin switching leading towards
ultrafast data writing. We use analytic theory and atomistic spin simulations
to discuss the behavior of ferromagnets and antiferromagnets in high-frequency
magnetic fields. In ferromagnets, linearly polarized fields align the
magnetization perpendicular to the external field, enabling $90^{\circ}$
switching. For circularly polarized fields in the $xy$ plane, the magnetization
tilts to the $z$ direction. During this tilting, it rotates around the $z$
axis, allowing $180^{\circ}$ switching. In antiferromagnets, external fields
with frequencies higher than the nutation frequency align the order parameter
parallel to the field direction, while for lower frequencies it is oriented
perpendicular to the field. The switching frequency increases with the magnetic
field strength, and it deviates from the Larmor frequency, making it possible
to outpace precessional switching in high magnetic fields.
