Structure dependent stray fields from domain walls in Permalloy films

Magnitudes and distributions of stray magnetic fields from a single domain wall in a Permalloy film are calculated for film thickness from 10 nm to 2.5 μm, using direct integration of the Landau-Lifshitz-Gilbert equation in a Cartesian lattice. This thickness range supports a Neel wall whose magnetization rotates in the plane of the film, a symmetric Bloch wall whose magnetization rotates out of the plane, and an asymmetric Bloch wall whose magnetization rotates simultaneously in and out of the plane of the film at the surfaces and inside the film, respectively. The stray field magnitude is largest for films with a Neel wall rather than film with a Bloch wall. The stray field magnitude varies linearly with thickness for films with Neel walls. The field distribution has a Neel-dominant character, i.e., it lies in a plane perpendicular to the plane of the wall, parallel to the plane of the film, and is dominated by the transverse component of the field. For films with a Bloch-type component, the stray field is lower. The field distribution has a Bloch-dominant character, i.e., it lies in a plane perpendicular to the plane of the wall, normal to the plane of film, and is dominated by the normal component of the field. At thickness larger than 1 μm, the stray field appears independent of thickness and is relatively constant at 15 Oe.