Magnetization reversal in patterned Co(0001) ultrathin films with perpendicular magnetic anisotropy

Using x-ray lithography we have patterned dot arrays in Au/Co/Au(111) sandwiches based on ultrathin Co layers with perpendicular anisotropy. Large area arrays of dots with diameters of 1 and 2 mu m have been obtained, keeping mostly undamaged the ultrathin Co layer. Hysteresis loops of the arrays depend drastically on the dot diameter. Magneto-optical domain visualization experiments confirm a magnetization reversal mechanism based on a large distribution of nucleation fields in the film, with complete reversal of the magnetization of one dot through the domain wall propagation after a local nucleation process. This could give information on the magnetization reversal processes in Au/Co/Au(111) continuous films. (C) 1996 American Institute of Physics.