Physical and magnetic properties of submicron lithographically patterned magnetic islands

We have developed a procedure for high-resolution patterning of magnetic thin films using direct-write electron beam lithography and a multistep sputter etching process [New et al., J. Vac. Sci. Technol. B 12, 3196 (1994)]. Using this patterning procedure we have defined large arrays of 0.2 by 0.4 μm magnetic islands out of a 200-Å-thick polycrystalline film of cobalt. The physical and magnetic structure of these islands has been examined using atomic and magnetic force microscopy, as well as transmission electron microscopy. Hysteresis loop measurements have been taken from large arrays of weakly interacting islands. The particles are not single domain and show considerable nonuniformity of magnetization when they are completely demagnetized. However, after application and removal of a large field along the long axes of the islands, most of the particles do relax into an almost uniform magnetization state.