  Magnetic skyrmions and their anti-particles, the antiskyrmions, are stable
magnetic solitons existing down to the nanometer scale. Their stability and
size as well as the possibility to propel them by, e.g., electric currents make
them promising candidates for the use in memory devices, such as racetrack
memories. Skyrmions and antiskyrmions share those same advantages individually,
but may annihilate each other when they coexist in the same device. Yet,
combining them to represent logical bits of 0 (skyrmion) and 1 (antiskyrmion)
in one device opens new possibilities to create new types of densely packed
racetrack memory devices. For this, a controlled creation and annihilation
procedure, i.e., a writing or deletion operation, is necessary. Here, we
propose a method to create arbitrary sequences of coexisting skyrmions and
antiskyrmions by rotations of the magnetic moments at the edge of a rectangular
slab. The skyrmions and antiskyrmions remain stable and do not annihilate each
other.
