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 disto rtion, by means of synchrotron radiation x-ray topography, complemented by Nomarski optical microscopy on the surface. After cooling through the Verwe y transition under a magnetic field parallel to [001], the images show a hi erarchy of domains. Domains associated with a small difference in lattice d istortion provide a clear indication that the symmetry is triclinic. They a ppear as a substructure of monoclinic domains separated by walls creating n o long-range stress. The domain structure deduced from the observation, und er the experimentally self-tested assumption that the walls involved are st ress free, is favorable from the elastic, magnetostatic, and electrostatic points of view. [S0163-1829(99)15201-9].