Abstract
The atom positions in antiferromagnetic and ferroelectric BiFeO3 have been obtained by profile analysis of powder neutron diffraction data collected ant 4.2K and 293K. The sublattice magnetization also determined at 4.2K, has been used to obtain a covalency parameter sum, Asigma 2+2Api 2+As2=13.4+or-0.5%. An experiment to obtain further information about the neutron magnetic form factor, by complete separation of the nuclear and magnetic contributions using polarization analysis, is described.