Electron Microscope Transmission Images of Coherent Domain Boundaries II. Observations

In part I of this paper the dynamic two‐beam theory of domain fringes was developed. In the present paper the properties of the fringe patterns, derived in part I, are observed and illustrated by means of examples. In particular, fringes resulting from ferroelectric domain‐walls in barium titanate, and anti‐ferromagnetic domain‐walls in nickel oxide, are discussed in detail. It is shown how from the nature of the first and last fringes, and a knowledge of the diffraction vector, the geometry of the domains on both sides of the domain wall can be deduced. In the case of barium titanate this procedure gives the direction of the tetragonal axes in both domains. In nickel oxide the directions of the contractions due to ferromagnetic ordering can be deduced. In niobium, domains can be produced by the insertion of gaseous interstitial impurities, which leads to a small deformation of the niobium matrix. The walls between such domains show the same type of fringes. Also the fringe patterns observed by Fourie et al. at twins in tin are discussed. Finally some numerical calculations based on the exact analytical expressions are compared with the observations and also with the approximate analytical treatment given in part I.