Rietveld Method Of La <sub> X </ Sub> Of Ca <sub>-the Xy </ Sub> Of Mno <sub> 3 </ Sub> And Y-<sub> X </ Sub> Ca <sub> 1-the Xy </ Sub> Of Mno <sub> 3 </ Sub> Crystal Structure

Manganites are prototypical of strongly-correlated electron systems where spin, charge, and orbital degrees of freedom are coupled. During the past ten years, rare-earth manganites have been receiving special attentions in the community of condensed matter physics owing to colossal magnetoresistance. We are convinced that the comprehension of complex problems posed by the manganites has the potential to produce a substantial advance in the theory of condensed matter physics, and will eventually shed light into other unsolved problems, for example, high-T_c superconductivity.In this article, some electron-doped powder samples of manganese oxides La_xCa_1-x-yMnO₃ (x=0.08,0.2) and Y_xCa_1-x-yMnO₃ (x=0.1,0.2) with A-site vacancy were synthesized using the solid-state reaction technique. The Rietveld refinements of powder X-ray diffraction patterns show that all the samples are single phase, with orthorhombic symmetry, and there is no change in structural symmetry at all the vacancy range from y=0 to y=0.2. The lattice parameters and volume of unit cell vary distinctly with y. We attribute these variations to the uncertain occupying ratio of vacancy at A-site and Mn-stie. The bond angle of Mn-O-Mn decreases with increasing y, which indicates the presence of Jahn-Teller effect in MnO₆ octahedron. On the contrary, σ² which reflects A-site cation disorder, increases linearly with vacancy level y. The unusual features of the electron-doped manganese oxides indicate that the lattice deformation directly influences the Mn-O bond length and Mn-O-Mn bond angle of MnO₆ octahedron. Structural analysis is of great importance to further study the transport and magnetic properties of these two electron-doped manganese oxides.