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 applied magnetic fields parallel (H∥) and perpendicular (H⊥) to the device’s electrodes. Different boundary conditions and dimensions have been examined. In most situations a Néel wall is formed in the constriction. When the size of the device is reduced (or the exchange stiffness is increased), then the energy barrier between the state with and without the Néel wall is increased. The domain wall magnetoresistance (DWMR) and anisotropic MR (AMR) have been estimated, and they show a maximum in the DWMR for both field directions of the applied magnetic field and a maximum and minimum in the AMR for H∥ and H⊥, respectively.