  Our measured dielectric constant and mechanical response of multiferroic
BiFeO3 indicate four phase transitions below room temperature. Features
correlate with those reported at 50K (from a peak in the zero-field-cooled
magnetic susceptibility) and 230K (from splitting between field-cooled and
zero-field-cooled magnetic data[1], and 200K (from magnon light scattering
cross sections[2]). The primary order parameter is not the polarization in any
of the low-T transitions. Instead, the transition near 230 K shows strong
elastic coupling, while that at 50K is fundamentally magnetic, but
magnetostrictively coupled to the the lattice. The low-T phase transitions
display glassy behaviour. A further anomaly at 140K interpreted as spin
reorientation[2,3] shows only weakly in dielectric and mechanical studies,
indicating that it is predominantly magnetic with little coupling to any of the
other order parameters.
