Dynamical Theory of the Images of Microtwins as Observed in the Electron Microscope

Abstract

Abstract In part II the dynamic two‐beam theory of the images of two superposed parallel coherent walls is presented. This situation occurs at overlapping ferroelectric and antiferromagnetic domain walls, enclosing microtwins characterized by very small twin vectors. In this paper the results deduced from the analytical theory developed in part II are compared with computed fringe profiles which are computed exactly. Very good agreement is found, in particular concerning the nature of the extreme fringes, the spacing and the contrast of the fringes, the mean intensities in the overlap and non‐overlap regions and the geometry of the image of a microtwin with increasing thickness. The results of the theory are illustrated by observations of plate‐ and wedge‐shaped microtwins in barium titanate and cobalteous oxide. It is found that the theoretical predictions about the features and general aspect of the images are supported by these observations.