Helical screw type magnetic structure of the multiferroic CaMn₇O₁₂ with low Cu-doping

The modulated crystal structure and modulated magnetic ordering of the multiferroic CaCu_xMn_7−xO₁₂ is studied by analysing neutron and synchrotron-radiation powder diffraction data with a model based on the magnetic superspace group R31′(00γ)ts.

Structure refinement and superspace description of the system Bi_2(n + 2)Mo_nO_6(n + 1) (n = 3, 4, 5 and 6)

The system of flexible composition Bi_2(n + 2)Mo_nO_6(n + 1) is described within the superspace formalism with two models, depending on the parity of the parameter n.

Unified (3 + 1)-dimensional superspace description of the 2212-type stair-like [Bi₂Sr₃Fe₂O₉]_m[Bi₄Sr₆Fe₂O₁₆] family of compounds

Two commensurate members (m = 4, 5) of the 2212 stair-like family of compounds with the composition [Bi₂Sr₃Fe₂O₉]_m[Bi₄Sr₆Fe₂O₁₆] have been analyzed and refined in the (3 + 1)-dimensional superspace framework. Both compounds are described by a unique model, including displacive modulations. The assumption of the validity of the proposed model for a range of compositions allows a realistic prediction of the structures of other members of the family.