Electron Holography of Nanoparticles

This thesis treats a number of aspects of electron holography. In conventional microscopy only the intensity of the object wave is recorded during the imaging process. The phase information is lost. The goal of (electron) holography is to record the phase so that all information contained in the original wave is measured. The general public knows holography mostly due to the three dimensional holograms that can be found e.g. on many credit cards. The most important application of electron holography is to study the electric and magnetic properties of materials. The electro-magnetic potential inside a material induces a phase shift on the electron wave. Thus measuring this phase shift gives direct information about the electric and magnetic properties of the material. During the Ph.D. period numerical methods were developed to simulate for a given material the hologram. These methods were then applied to a number of common magnetic structures. This is an example of the direct problem: given a magnetization distribution compute the hologram. Much more important is the inverse problem: given a phase distribution what was the magnetization distribution. In the thesis a number of methods were evaluated to solve this problem. This thesis also reports results of a number of experiments performed on ferromagnetic films and cobalt clusters. The results were analyzed using the methods from this thesis.