Tracking the local reversal processes in nanostructures by magnetic speckles

Abstract

We have used coherent soft x-ray resonant magnetic scattering to locally track reversal processes in magnetic nanostructures. Coherent illumination of a limited number of nano-objects in a CoPt nanoline grating produces a specific speckle pattern, whose evolution under in situ magnetic field reveals the true local magnetic ordering. While each nanoline behaves as a single macrospin whose direction depends on the dipolar coupling with neighbors, the global reversal of the line array is successively governed by two effects: first, by the random distribution of defects, followed by the dipolar coupling favoring antiferromagnetic ordering.