Role of boundary conditions and dimensions on the micromagnetics of a cobalt point contact

We have calculated the micromagnetic structure of a Co point contact, for a pplied magnetic fields parallel (H-parallel to) and perpendicular (H-perpen dicular to) to the device's electrodes. Different boundary conditions and d imensions have been examined. In most situations a Neel wall is formed in t he constriction. When the size of the device is reduced (or the exchange st iffness is increased), then the energy barrier between the state with and w ithout the Neel wall is increased. The domain wall magnetoresistance (DWMR) and anisotropic MR (AMR) have been estimated, and they show a maximum in t he DWMR for both field directions of the applied magnetic field and a maxim um and minimum in the AMR for H-parallel to and H-perpendicular to, respect ively. (C) 1999 American Institute of Physics. [S0021-8979(99)34208-0].