Variable temperature powder neutron diffraction study of the Verwey transition in magnetite Fe3O4

Neutron powder diffraction data have been collected from a sample of polycrystalline Fe3O4. High resolution data collected at 60 K are fitted using a simple rhombohedral distortion of the cubic unit cell. This model accounts for all of the peak splittings that occur upon cooling through the Verwey transition temperature (TV). Lower resolution data collected between 2 and 280 K are fitted using the same model, which gives TV = 110 +- 5 K. These data show a change in the thermal expansion due to the softening of phonons above TV and a change in crystallite extinction arising from twinning at the transition.