  The pinning effect of the periodic diameter modulations on the domain wall
propagation in FeCoCu individual nanowires is determined by Magnetic Force
Microscopy, MFM. A main bistable magnetic configuration is firstly concluded
from MFM images characterized by the spin reversal between two nearly single
domain states with opposite axial magnetization. Complementary micromagnetic
simulations confirm a vortex mediated magnetization reversal process. A refined
MFM imaging procedure under variable applied field allows us to observe
metastable magnetic states where the propagating domain wall is pinned at
certain positions with enlarged diameter. Moreover, it is demonstrated that in
some atypical nanowires with higher coercive field it is possible to control
the position of the pinned domain walls by an external magnetic field.
