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Dynamical Theory of the Images of Microtwins as Observed in the Electron Microscope. II. Overlapping Domain Wall Boundaries
Author(s) -
Remaut G.,
Gevers R.,
Lagasse A.,
Amelinckx S.
Publication year - 1965
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.19650100113
Subject(s) - crystal twinning , reflection (computer programming) , condensed matter physics , transmission electron microscopy , stacking fault , facet (psychology) , orientation (vector space) , dislocation , optics , psychology , crystallography , chemistry , microstructure , geometry , physics , personality , computer science , programming language , mathematics , social psychology , big five personality traits
The two‐beam dynamic theory of the electron transmission microscopic fringe images of microtwins is discussed. In contrast to Part I, it is now assumed that the parent crystal and microtwin are both close to an orientation for reflection. The excitation errors are then slightly different. This situation occurs in BaTiO 3 , CoO, NiO, where the twins are ferro‐electric or anti‐ferromagnetic domains characterized by small twin‐vectors and limited by parallel coherent boundaries inclined with respect to the foil surfaces. If the thickness of the microtwin is small, the anomalous absorption for the microtwin can be neglected. It can then be shown that the images are similar to stacking fault images defined by a phase angle depending on the diffraction conditions and on the microtwin thickness. For a thick microtwin, it can be shown that the part of the images where the boundaries overlap can be differentiated very well from the non‐overlapping parts. An analytical discussion leads to several significant conclusions regarding the nature of the extreme fringes, the contrast of the fringes, and the mean intensities. In Part III these predictions will be compared with the results of numerical calculations. It will be also shown that they are in good agreement with experiment.