  Magnetic skyrmions, vortex-like swirling spin structures with quantized
topological number, observed in chiral magnets, are appealing for potential
applications in spintronics because it is possible to control their motion with
ultralow current density. In order to realise skyrmion-based spintronic
devices, it is essential to understand the skyrmion motions in confined
geometries. Here we show by micromagnetic simulations that the current-induced
motion of skyrmions in the presence of geometrical boundaries is very different
from that in an infinite plane. In a channel with finite width, the transverse
confinement results in steady state characteristics of the skyrmion velocity as
a function of current similar to those of domain walls in ferromagnets, whereas
the transient behaviour depends on the initial distance of the skyrmion from
the boundary. In addition, we show that single skyrmions can be created by
electric current in a simple constricted geometry of a plate-shaped specimen of
suitable size and geometry. These findings could guide the design of
skyrmion-based devices, in which skyrmions are used as information carriers.
