  We consider current-driven motion of magnetic skyrmions in granular magnetic
films. The study uses micromagnetic modeling and phenomenological analysis
based on the Thiele formalism. Remarkably, disorder enhances the effective
skyrmion Hall effect that depends on the magnitude of the driving force
(current density and non-adiabaticity parameter). The origin is sliding motion
of the skyrmion along the grain boundaries, followed by pinning and depinning
at the grain junctions. A side-jump can occur during this depinning process. In
addition, the critical current that triggers the skyrmion motion depends on the
relative size of the crystallites with respect to the skyrmion size. Finally,
when the skyrmion trajectory is confined along an edge by the non-adiabatic
Magnus force, the critical current density can be significantly reduced. Our
results imply that narrow nanowires have higher skyrmion mobilities.
