Domains in the low-temperature phase of magnetite from synchrotron-radiation x-ray topographs

Domains in the low-temperature, ferrimagnetic, and ferroelectric, phase of magnetite Fe₃O₄ were investigated in the bulk, via their ferroelastic distortion, by means of synchrotron radiation x-ray topography, complemented by Nomarski optical microscopy on the surface. After cooling through the Verwey transition under a magnetic field parallel to [001], the images show a hierarchy of domains. Domains associated with a small difference in lattice distortion provide a clear indication that the symmetry is triclinic. They appear as a substructure of monoclinic domains separated by walls creating no long-range stress. The domain structure deduced from the observation, under the experimentally self-tested assumption that the walls involved are stress free, is favorable from the elastic, magnetostatic, and electrostatic points of view.