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 (T_V). Lower resolution data collected between 2 and 280 K are fitted using the same model, which gives T_V=110±5 K. These data show a change in the thermal expansion due to the softening of phonons above T_V and a change in crystallite extinction arising from twinning at the transition.