Using the Gauss-Seidel projection method developed in  and
, we simulate the three dimensional domain wall structures for
thin films at various thickness. We observe transition from Néel
wall to cross-tie wall and to Bloch wall as the thickness is
increased. Periodic structures for cross-tie wall are also studied.
The results are in good agreement with the experimental
observations. Hysteresis loops are calculated for samples of various
sizes. In particular, we study the effect of cross-tie wall in the
switching process. These simulations have demonstrated high
efficiency of the Gauss-Seidel projection method.