Observation of a geometrically constrained domain wall in epitaxial FCC Co small disks

The magnetic nanostructure of epitaxial FCC Co/Cuð0 0 1Þ circular elements (B1:7 mm in diameter) has been imaged with scanning electron microscopy with polarisation analysis. A closed flux configuration (quadrant configuration) is observed for most of the disks, characteristic of systems with cubic anisotropy. However, the measured width of the 90 domain wall varies with the distance from the vortex core, from 70725 nm up to a value determined by the disk radius. Such a wide domain wall is a consequence of the geometrical constraints imposed by the element, thus defining a geometrically constrained domain wall, as confirmed by micromagnetic simulations. r 2003 Elsevier B.V. All rights reserved. PACS: 75.60.Ch; 75.25.+z; 75.40.Mg; 75.70. i