Non-stoichiometric La <sub> 0.67 </ Sub> Of Sr <sub> 0.33-x </ Sub> ¡õ <sub> X </ Sub> Structure And Transport Properties Of Mno <sub> 3 </ Sub> Research,

Rare-earth manganites have been receiving special attentions in the community ofcondensed matter physics owing to colossal magnetoresistance. The carrier has highpolarization and they have giant magnetoresistance around T_C. In other hand, manganitesare prototypical of strongly-correlated electron systems in which spin, charge, and orbitaldegrees of freedom are coupled. We are convinced that the comprehension of complexproblems posed by the manganites has the potential to produce a substantial advance in thetheory of condensed matter physics, and will eventually shed light into other unsolvedproblems, for example, high-T_C superconductivity.In this article, some hole-doped bulk samples of manganese oxidesLa_0.67Sr_0.33-xâ–¡_xMnO₃ (x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.33) with A-site vacancy weresynthesized using the solid-state reaction technique. The Rietveld refinements of powderX-ray diffraction patterns show that all the samples are single phase, with rhombohedralsymmetry, and space group R(?)c. There is no change in structural symmetry at all thevacancy range from x=0 to x=0.33. The lattice parameters and volume of unit cell varydistinctly with x. We attribute these variations to the uncertain occupying ratio of vacancyat A-site and Mn-site. The bond angle of Mn-O-Mn decreases with increasing x, whichindicates the presence of Jahn-Teller effect in MnO₆ octahedron. On the contrary,σ²,which reflects A-site cation disorder, increases linearly with vacancy level x. The unusualfeatures of the hole-doped manganese oxides indicate that the lattice deformation directlyinfluences 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 magneticproperties of these hole-doped manganese oxides. Electrical measurements ofLa_0.67Sr_0.33-xâ–¡_xMnO₃ show that the samples exhibit a metallic-semiconducting transitionwhen x＜0.25, and the effect of the magnetic field is to lower the value of the resistivity butmake T_C shift to higher temperature. In the range of 0.25≤x≤0.33, the samples exhibitinsulating property, and also the effect of the magnetic field is to lower the value of theresistivity.