Bulk domain analysis in iron (111) crystals

The thickness dependence of the domain width of a wedge-shaped, (111)-oriented Fe_87.2Si_12.8 crystal is experimentally determined by Kerr microscopy and metallographic analysis. The FeSi alloy was chosen because it allows bulk domain observation by "freezing-in" the domains as a submicroscopic precipitation pattern by heat treatment at 580°C. The complete topology of the domains (present during annealing) can then be analyzed at room temperature by cutting the crystal and imaging in a polarization microscope, making use of a birefringence effect that arises from the precipitations after etching.