Colossal Magnetoresistance Materials La-ca - Mn-fe-o Neutron Diffraction Study

In this thesis, a series of perovskite-type manganite Lai.xCaxMno96Feo.o403 (x=0.31,0.5,0.6) were studied by neutron power diffraction, and the crystal structure,atom positions were obtained by Rietveld refinement method. Meanwhile, the relation between the structure and properties of these samples were discussed as well.The mixed valence perovskite-type manganite polycrystalline samplesLai_xCaxMno.96Feo.o4C>3 (x=0.31,0.5,0.6) were prepared using a standard solid-state reactionmethod. The neutron powder diffraction data was collected at room temperature. The crystallographic structures of perovskite-type manganites La1.xCaxMno96Feo.04O3(x=0.31,0.5,0.6) were refined by Rietveld profile refinement program Rietica and Fullprof.The refined results show that Lai_xCaxMno.96Feo.o4C>3 (x=0.31,0.5,0.6) compoundsexhibit the orthorhombic GdFeC>3 structure, the space group is Pnma, including MnC>6 type octahedron. The La/Ca atoms prefer to 4c sites, the Mn/Fe atoms prefer to 4b sites, the O atoms prefer to 4c and 8d sites. The bond lengths of Mn-0 and the bond angles of Mn-O-Mn are calculated. The bond lengths and the bond angles are changed with the incoming of the content Ca. The relation between the trend of the bond lengths and angles and the magnetic property was discussed.