The The Cacu <sub> X </ Sub> Of Mn <sub> 3-x </ Sub> Mn <sub> 4 </ Sub> O <sub> 12 </ Sub> Structure And Magnetoresistance Of Nature

[AC₃](B₄)O₁₂ series materials have large low field magnetoresistance and welltemperature stability,but the study of these series materials are less relavitely and aboutthe principle of CMR unclearly. In this article, the sample ofCaCu_xMn_3-xMn₄O₁₂(x=0.2,0.4,0.6,0.8,1.0,1.2,1.4) synthesized using wet-chemistrytechnique, and then sinter in higher temperature, further enrich the research of seriesmaterials.The Rietveld refinements of powder X-ray diffraction pattems show that all thesamples are single phase, with cubic symmetry, the space group Im3 and there is nochange in structural symmetry at all the copper ion composition range from x=0.2 to x=1.4.The lattice parameters and volume of unit cell decrease with increasing doping level x.Although the radius of Cu²⁺ is larger than that of Mn³⁺, Mn³⁺ turns into Mn⁴⁺ partially andthe radii of Mn⁴⁺ smaller than that of Mn³⁺, but the latter reason plays the main role,thuscause the volume of unit cell to increase. The bond angle of Mn2-O-Mn2 changesrulelessly with increasing x, which indicates the presence of Jahn-Teller effect in MnO₆octahedron. The reason of these results is the mismatch between Jahn-Teller ionsMn³⁺/Cu²⁺.The unusual features of the manganese oxides indicate that the latticedeformation directly influences the bond length and angle of MnO₆ octahedron. Structuralanalysis is of great importance to further study the transport and magnetic properties ofthese manganese oxides. In addition, we studied the CMR effect of these sample and findthat the MR increases with increasing x and reach the maximum at x=1.0, then presentsdecreasing trend in the field of 5T. But at low-magnetic-field the resistivity changesindistinctly, these because of the spin-polarized scatter of carriers between grains anddouble-exchange effect.