In-situ Lorentz microscopy and Lorentz phase imaging of artificially structured Co arrays

Abstract

We combined in-situ magnetizing experiments with Lorentz Fresnel microscopy and Lorentz phase microscopy to analyse both qualitatively and quantitatively the in-situ magnetization process of artificially structured two dimensional arrays of Co islands. A newly developed Lorentz phase microscopy allows detailed mapping of in-plane magnetization on a nanometre scale following the hysteresis loop. For polycrystalline Co films, 20–40 nm thick, we observed four major steps in the magnetization process: coherent spin rotation in adjacent nanodomains, nucleation of reverse domains, motion of the domain walls and additional spin rotation in magnetic domains and, finally, an expulsion of energetically non-favourable domains followed by the domain wall annihilation at the edges of Co islands. We offer a clear physical explanation of the magnetization ripple contrast.