Micromagnetics and magnetoresistance of a Permalloy point contact

We performed micromagnetic calculations for a Permalloy point contact. The magnetization configurations show the formation of a Néel wall in the constriction. The occurrence of a Néel wall instead of a Bloch wall results from the dipole–dipole energy in this region. The evolution of the magnetization with field differs strongly for fields parallel and perpendicular to the electrodes. In the former case, the pattern evolves abruptly and in a narrow range, while in the latter case it evolves smoothly and in a rather wide range. From the magnetization patterns, we estimate the domain-wall magnetoresistance and the anisotropic magnetoresistance, which we compare with experimental data.