Long range ordering of two transition metal charge (oxidation) states occurs in many oxides. Direct structural evidence from powder neutron diffraction studies on several half-doped manganites (Pr0.5Ca0.5MnO3, TbBaMn2O6, YBaMn2O6) and magnetite (Fe3O4) is reviewed. Charge ordering is accompanied by subtle distortions to low (monoclinic or triclinic) symmetry in all cases. The half-doped manganites reveal polymorphism of both charge and Mn3+ orbital ordered arrangements. The degree of charge separation estimated by bond valence sums for these and other oxides is only 20-80% of the ideal difference. The origin of this effect is not clear from present data. (c) 2006 Elsevier SAS. All rights reserved.
|Number of pages||7|
|Journal||Solid state sciences|
|Publication status||Published - Aug 2006|
- LOW-TEMPERATURE STRUCTURE
- VERWEY TRANSITION
- MAGNETITE FE3O4