Oxygen Ordered Phases in La_xSr_1−xMnO_y (0 ≤ x ≤ 0.2, 2.5 ≤ y ≤ 3): An In situ Neutron Powder Diffraction Study

Abstract

In situ neutron powder diffraction experiments have been performed on samples of SrMnO y , La 0.1 Sr 0.9 MnO y , and La 0.2 Sr 0.8 MnO y (2.5 e y e 3) to determine the existence of oxygen-vacancy ordering and study order-disorder transformations in the La x Sr 1-x MnO y system. The vacancy ordered monoclinic Sr 7 Mn 7 O 13 , tetragonal (La x Sr 1-x ) 5 Mn 5 O 13 and orthorhombic (La x Sr 1-x ) 2 Mn 2 O 5 (x ) 0, 0.1, and 0.2) phases have been observed, together with already described La 0.1 Sr 0.9 MnO 2.55 . Reversible vacancy order-disorder transitions have been observed for the La-containing (La x Sr 1-x ) 5 Mn 5 O 13 phases. Oxygen-vacancy disordered cubic or pseudocubic phases have also been observed with increasing stability range in y with increasing x. Preliminary phase diagrams of the system have been derived as a function of temperature and oxygen content.

The synthesis and complex anion-vacancy ordered structure of La0.33Sr0.67MnO2.42

“…2 [11][12][13]. In order to determine if the observed higher oxidation states and lower anion deficiency of strontium rich La 1À x Sr x MnO 3À y phases indicates a stability boundary, or only that a more powerful chemical agent is required to reduce these phases, we undertook a study of the topotactic reduction chemistry of La 1À x Sr x MnO 3 (x40.5) substrates with the powerful solid-state reducing agent NaH [14].…”

Research Update: Plentiful magnetic moments in oxygen deficient SrTiO3

“…Neutron powder diffraction combined with synchrotron X-ray diffraction techniques has been used to determine the structure of complex-oxide Ti-based structures identifying vacancy ordering arrangements in bulk samples. 5 Switching on/off behavior in TiO 2 -based resistive-random-access-memories has been found to be driven by the formation and disruption of conducting filaments of Ov. 6 Experimental techniques to increase or deplete charge carrier density Ov-rich areas allow the emergence of magnetic phases in STO based compounds.…”

Understanding the interactions between oxygen vacancies atSrTiO3(001) surfaces

“…However, experiments also indicate the presence of ordered vacancies, both in bulk perovskite oxides and at oxide heterostructures. [15][16][17][18][19] Regions with ordered oxygen vacancies in YMnO 3 are found to be conducting, 20 implying that ordered vacancies may also be metallic. A theoretical study of oxygen vacancies in bulk CaMnO 3 suggests that the ordering of vacancies is favored at finite temperatures.…”

“…In addition, all possible divacancy arrangements lead to the emergence of 2DEGs; thus explaining the increased conductivity observed in oxide heterostructures grown under oxygen poor conditions that also show ordered vacancy arrangements. 15,16,20 The largest contribution to the 2DEG is mainly from the pristine TiO 2 layer closest to the defective layer. The SrO-layer never contributes to the metallicity due to its intrinsic ionicity.…”