  In skyrmion-based racetrack memories, the information encoded by skyrmions
may be destroyed due to the skyrmion Hall effect, which can be surmounted by
using synthetic antiferromagnetic racetracks. Hence, the manipulation of
skyrmions in synthetic antiferromagnetic racetracks is important for practical
applications. Here, we computationally study the interaction between a pair of
skyrmions and a locally modified region in a synthetic antiferromagnetic
racetrack, where the perpendicular magnetic anisotropy or thickness is locally
adjusted to be different from that of the rest region of the racetrack. It is
found that the skyrmions can be attracted, repelled, and even trapped by the
locally modified region in a controllable manner. Besides, we demonstrate that
the skyrmion location can be precisely determined by the locally modified
region. The possible manipulation of skyrmions by utilizing locally modified
regions in a synthetic antiferromagnetic racetrack may be useful for future
skyrmion-based applications.
