The propagation of a single magnetic Bloch domain wall (DW) in a mesoscopic
wire is studied by use of the extraordinary Hall effect. Whereas a straigh
t DW propagates freely in a wire with constant lateral width, the propagati
on in a Hall cross reveals that both DW shape and DW velocity vary strongly
as a function of DW position. These results give the first experimental ev
idence that the dynamical properties of a magnetic DW in a patterned struct
ure are strongly affected by the device geometry. This has to be taken into
account for future applications to spin electronic devices.