Complex manganese oxides with the brownmillerite structure: Synthesis, crystal chemistry and properties

Structural features and synthetic schemes of complex manganese oxides with the brownmillerite structure A(2)MnB'O5+delta (A=Ca, Sr; B'=Ga, Al) and their derivatives are analysed. Modem approaches to the description of structures containing different types of chains of tetrahedra are considered; patterns of ordering of such chains are discussed. The influence of the electronic structure and crystal-chemical properties of the B' cations on the possibility of formation of a layered ordered structure is noted. The attention is focused on the anionic non-stoichiometry of brownmillerite phases and the effect of overstoichiometry oxygen (fluorine) on the structure of compounds. Comparative analysis of the propetries of oxygen- and fluorine-doped brownmillerites is given. The data on the magnetic structure and transport and magneto resistive properties of Mn-containing brownmillerites are generalised.