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 Neel wall in the const riction. The occurrence of a Neel wall instead of a Bloch wall results from the dipole-dipole energy in this region. The evolution of the magnetizatio n with field differs strongly for fields parallel and perpendicular to the electrodes. In the former case, the pattern evolves abruptly and in a narro w range, while in the latter case it evolves smoothly and in a rather wide range. From the magnetization patterns, we estimate the domain-wall magneto resistance and the anisotropic magnetoresistance, which we compare with exp erimental data. (C) 1999 American Institute of Physics. [S0003-6951(99)0110 3-1].