  We have studied nucleation of magnetic domains and propagation of magnetic
domain walls (DWs) induced by pulsed magnetic field in a ferromagnetic film
with in-plane uniaxial anisotropy. Different from what have been seen up to now
in out-of-plane anisotropy films, the nucleated domains have a rectangular
shape in which a pair of the opposite sides are perfectly linear DWs, while the
other pair present zigzags. This can be explained by magnetostatic
optimization, knowing that the pulse field is applied parallel to the easy
magnetization axis. The field induced propagation of these two DW types are
very different. The linear ones follow a creep law identical to what is usually
observed in out-of-plane films, when the velocity of zigzag DWs depends
linearly on the applied field amplitude down to very low field. This most
unusual feature can be explained by the shape of the DW, which makes it
possible to go round the pinning defects. Thanks to that, it seems that
propagation of zigzag walls agrees with the 1D model, and these results provide
a first experimental evidence of the 1D model relevance in two dimensional
ferromagnetic thin films. Let's note that it is the effective DW width parallel
to DW propagation direction that matters in the 1D model formula, which is a
relevant change when dealing with zigzag DWs.
