4. Electron holography and its application to magnetic materials

Abstract

The transmission electron microscope (TEM) is widely used for characterizing the microstructure of materials, and there are several imaging modes that are sensitive to magnetic microstructure. Electron holography is an alternative TEM technique that provides access to the phase and amplitude of an electron wave after it has traversed through the sample. This chapter describes the development of electron holography and the basic principles of the technique with particular reference to magnetic imaging. Some applications of electron holography are discussed in the chapter, which include the studies of hard magnets, magnetic media, and magnetic microstructures. The chapter also discusses prospects for the further development of the technique, such as real-time viewing of dynamic events and the in situ application of variable external fields. Off-axis electron holography offers the prospect of direct visualization and quantification of magnetic fields with high spatial resolution and sensitivity. The theoretical framework of the technique is well established, and experimental applications to important materials problems are presented in the chapter.