A New Ordered Oxygen-Deficient Manganite Perovskite:  LaBaMn2O5.5. Crystal and Magnetic Structure

• Published in: Chemistry of materials 1999-04, Vol.11 (4), p.930-938
• Main Authors: Caignaert, V, Millange, F, Domengès, B, Raveau, B, Suard, E
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Inorganic compounds; Magnetic properties and materials; Physics; Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.); Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Water, oxides, hydroxides, peroxides
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/cm980469h

A new ordered oxygen-deficient perovskite, LaBaMn2O5.5, has been synthesized, using the topotactic deoxygenation of the ordered LaBaMn2O6 perovskite. The crystal structure of this manganite was solved in the space group Ammm (a = 3.86 Å, b = 8.19 Å, c = 15.47 Å) from neutron powder diffraction data. The [Mn2O5.5]∞ framework is build up of row of MnO6 octahedra and MnO5 pyramids running along a⃗. This structure is intermediate between that of the ordered LaBaMn2O6 perovskite and that of LaBaMn2O5:  it consists of ordered barium and lanthanum layers stacked alternatively along c⃗, oxygen vacancies being located at the level of the La layers. The magnetic structure is original:  manganese spins form ferromagnetic spin-ladders along the b⃗ axis that are antiferromagnetically coupled along the a⃗ and c⃗ axis. The HREM investigation shows the existence of 90° oriented domains and twinning phenomena.