Domain structure and colossal magnetoresistance of La{sub 1{minus}x}Sr{sub x}CoO{sub 3} and La{sub 1{minus}x}Ca{sub x}MnO{sub 3}

La{sub 1{minus}x}Sr{sub x}CoO{sub 3} (LSCO) and La{sub 1{minus}x}Ca{sub x}MnO{sub 3} (LCMO) are a class of magnetic oxides exhibiting the colossal magnetoresistance (CMR) effect. However, the CMR ratio of LSCO is much lower than that of LCMO. Microstructure studies were carried out to understand this difference. In La{sub 0.5}Sr{sub 0.5}CoO{sub 3} (LSCO), an ordered, anisotropic perovskite-type structure n-LSCO was observed. The ordered structure has a tetragonal cell with a La-Co-Sr-Co- [001] layered atom distribution along the c-axis. This new structure is intrinsic for the LSCO system and is a direct result of the lattice substitution between La and Sr. The entire film is composed of [001], [010] and [100] anisotropic domains with sizes on the order of 30--200 nm. The La{sub 0.7}Ca{sub 0.3}MnO{sub 3} (LCMO) film, however, does not exhibit a domain structure. It is concluded that the domain structure may have negative effect on the CMR ratio.