Crystal structure and spiral magnetic ordering of BiFeO3 doped with manganese

Neutron powder diffraction has been performed on polycrystalline BiMnxFe1-xO3 (x = 0, 0.1 and 0.2). The structures of the doped compounds are described by the space group R3c of ferroelectric BiFeO3. Refined structure parameters are presented. Mn doping generates microstructural changes manifested by broadening in the diffraction patterns. The lattice parameters show a non-linear behaviour from 4 K to 630 K. Mn doping results in a transformation of the long-range spiral spin modulation of BiFeO3 to a collinear anti-ferromagnetic structure with spins along c. The average magnetic moments and the ordering temperatures decrease with increasing Mn concentration.