title: Large oxygen nonstoichiometry in La(0.77)Sr(3.23)Co(2.75)C(0.25)O(8.40+δ) oxide (δ = 0, 1.3) related to n = 3 RP series.
abstract: An original Ruddlesden-Popper phase, La(0.77)Sr(3.23)Co(2.75)C(0.25)O(8.40+δ), was isolated and studied by electron, X-ray, and neutron diffraction. This structure has complex crystal chemistry resulting from a high degree of flexibility in the structure, comprising the disordered introduction of carbonates into a cobalt layer and an important oxygen deficiency with a preferential repartition of vacancies along the layers stacking sequence. The former is necessary for the stabilization of the system, while the latter can be tuned by postsynthetic treatment, yielding in a large variety of cobalt species formal oxidation states ranging from Co(2+)/Co(3+) in the as-made phase to Co(3+)/Co(4+) when annealed under oxygen pressure. The potential richness deriving from this flexibility is illustrated in terms of the magnetotransport properties and includes a resistivity that varies within a range of 5 orders of magnitude after modulation of the oxygen content with the appearance of negative magnetoresistance and ferromagnetic interactions due to Co(3+)/Co(4+) mixed-valence state.
authors: Laboratoire CRISMAT, UMR CNRS-ENSI Caen 6508, 6 bd Maréchal Juin, 14050 CAEN Cedex, France.
authors: A
authors: A
authors: Demont
authors: S
authors: S
authors: Hébert
authors: J
authors: J
authors: Höwing
authors: Y
authors: Y
authors: Bréard
authors: D
authors: D
authors: Pelloquin
mesh_terms: D002244:Carbon / Q000737:chemistry*; D003035:Cobalt / Q000737:chemistry*; D007811:Lanthanum / Q000737:chemistry*; D033363:Neutron Diffraction; D010087:Oxides / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D013324:Strontium / Q000737:chemistry*
chemical_list: D010087:Oxides; D003035:Cobalt; D007811:Lanthanum; D002244:Carbon; D010100:Oxygen; D013324:Strontium