%0 Journal Article
%A González Merchante, Daniel
%A Cortés Gil, Raquel
%A Alonso Rodríguez, José María
%A Matesanz Sáez, Emilio
%A Rivera Calzada, Alberto Carlos
%A Santamaría Sánchez-Barriga, Jacobo
%A Ruiz González, María Luisa
%A González Calbet, José María
%T Complex structural ordering of the oxygen deficiency in La_-0.5 Ca_2.5Mn_2O_7-delta Ruddlesden-Popper phases
%D 2019
%@ 2053-2733
%U https://hdl.handle.net/20.500.14352/13640
%X Ruddlesden-Popper oxides, (AO)(ABO_3))_n, occupy a prominent place in the landscape of materials research because of their intriguing potential applications. Compositional modifications to the cation sublattices, A or B, have been explored in order to achieve enhanced functionalities. However, changes to the anionic sublattice have been much less explored. In this work, new oxygen-deficient manganese Ruddlesden-Popper-related phases, La_0.5Ca_2.5Mn_2O_6.5, and La_0.5Ca_2.5Mn_2O_6.25, have been synthesized by controlled reduction of the fully oxidized n = 2 term La_0.5Ca_2.5Mn_2O_7. A complete structural and compositional characterization, by means of neutron diffraction, electron diffraction and atomically resolved scanning transmission electron microscopy and electron energy-loss spectroscopy techniques, allows the proposition of a topotactic reduction pathway through preferential oxygen removal in the [MnO_2] layers along [031] and [013] directions. The gradual decrease of the Mn oxidation state, accommodated by short-range ordering of anionic vacancies, reasonably explains the breaking of ferromagnetic interactions reinforcing the emergence of antiferromagnetic ones. Additional short-range order-disorder phenomena of La and Ca cations have been detected in the reduced La_0.5Ca_2.5Mn_2º_7-delta, as previously reported in the parent compound.
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