Transitional domain wall structure in Permalloy magnetic films with decreasing thickness

The transitional wall structure of a domain wall in Permalloy films in the thickness range of 5.12 μm to 0.16 μm is investigated using direct integration of the Landau-Lifshitz-Gilbert equation in a three dimensional Cartesian lattice. The expected stray-field-free structure containing a Bloch wall in the center, Neel caps at the surfaces with a vortex structure on one side of the wall was found for films thicker than 2.56 μm. However, the region through the thickness where the ∇^ω·M^μ across the wall is zero (Bloch wall) was of small extent below 1 μm thickness. Neel caps with opposite chirality existed at all thickness investigated down to 0.16 μm. The vortex is characterized by an overshoot in the polar angle θ out of the plane of the material. Two maximum values of the overshoot were observed for films 2.56 μm and thicker. They were located near the film surface under the Neel caps. Thinner films had only one maximum located in the center of the material. The maximum overshoot was a function of thickness varying from 100 to a maximum value of 340 for the 0.64 μm thick sample. As the thickness is decreased to 0.16 μm, a residual normal component is observed at the surface near the Neel caps, leading to stray fields at the surface