STUDY OF CO, NI AND CO CU NANOWIRES - MAGNETIC-FLUX IMAGING BY OFF-AXIS ELECTRON HOLOGRAPHY/

The potential of electron holography for determining the remanent magn etisation state of small particles is illustrated by the study of nano meter-sized cylindrical model structures. The leaking flux was imaged for ferromagnetic Co and Ni wires of radius ranging from 20 to 150 nm and of a length of a few microns. For the smallest radius, the remanen t magnetisation state was found to be uniform along the wire axis, wit h a value corresponding to the saturation magnetisation. For larger ra dii, nonuniform magnetisation configurations begin to appear, in gener al evidenced by the magnetisation value smaller than the saturation va lue. In a few cases multidomain wires were observed where a fraction s howed an opposite magnetisation. Nanowires formed by a succession of e longated Co grains separated by Cu showed several magnetic configurati ons, from the parallel ferromagnetic alignment of the magnetic grains to the antiparallel configuration along the wire.