Electron images of domain walls in cobalt foils

Abstract

The images of domain walls in thin sections of cobalt, produced by the Fresnel mode of Lorentz electron microscopy, have been calculated by wave-optical theory. Using a single 180° wall model of the object the image has been calculated for various values of θ, where θ is the angle between the domain magnetization and the surface of the specimen. An object consisting of a periodic array of walls has also been considered and the image calculated for θ=π/2. In this case, for specific values of defocusing distance it is possible to obtain the phase transmission function of the object as a simple function of the intensity in the image. Qualitative comparison of the experimental images of domain walls in cobalt crystals is made with those obtained by theory for 0<θ≤π/2. Quantitative comparison of theory and experiment for θ=0 enables the domain wall widths to be determined. The wall widths are compared with theoretical estimates.