  Skyrmion-containing devices have been proposed as a promising solution for
low energy data storage. These devices include racetrack or logic structures
and require skyrmions to be confined in regions with dimensions comparable to
the size of a single skyrmion. Here we examine Bloch skyrmions in {FeGe} device
shapes using Lorentz transmission electron microscopy (LTEM) to reveal the
consequences of skyrmion confinement in a device structure. Dumbbell-shaped
devices were created by focused ion beam (FIB) milling to provide regions where
single skyrmions are confined adjacent to areas containing a skyrmion lattice.
Simple block shapes of equivalent dimensions were prepared within the specimen
to allow a direct comparison with skyrmion formation in a less complex, yet
still confined, device geometry. The impact of the application of an applied
external field and varying the temperature on skyrmion formation within the
shapes was examined and this revealed that it is not just confinement within a
small device structure that controls the position and number of skyrmions, but
that a complex device geometry changes the skyrmion behaviour, including
allowing formation of skyrmions at lower applied magnetic fields than in simple
shapes. This could allow experimental methods to be developed to control the
positioning and number of skyrmions within device shapes.
