Local lattice distortions due to growth striations near the surface of flux-grown (PbO/PbF 2) (111) yttrium iron garnet crystals (YIG) and Ga-substituted yttrium iron garnet crystals (Ga-YIG) were studied by means of double-crystal X-ray reflection topography. Topographic contrast of growth striations could be separated into those caused by local variations of lattice spacing and those due to local misorientations of the lattice planes at the boundaries. The results are in good agreement with calculated lattice constant profiles and a relaxation model of bulk stresses at the crystal surface. Assuming equivalent amounts of the main impurities Pb and F the lattice constant profiles were calculated taking into account the local concentrations of Pb or Pb and Ga, respectively, which were determined by step scan measurements with an electron probe microanalyzer (EPMA).
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