Structure and microstructure of ${\mathrm{La}}_{1-x}{\mathrm{Ca}}_x{\mathrm{MnO}}_{3\mathrm{-}\mathrm{\delta }}$ thin films prepared by pulsed laser deposition

${\mathrm{La}}_{1-x}{\mathrm{Ca}}_x{\mathrm{MnO}}_{3\mathrm{-}\mathrm{\delta }}$ (LCMO) thin films are grown by pulsed laser deposition on a (100) ${\mathrm{SrTiO}}_3$ substrate at temperatures between 530 and 890 °C. The magnetotransport properties show a high negative magnetoresistance and a shift of the maximum of the $R\left(T\right)\mathrm{}$ curve as a function of temperature. The Curie temperature changes with deposition temperature and film quality in the range of 100–220 K. The film quality is characterized by x-ray diffraction and transmission electron microscopy (TEM); film and target compositions were verified by atomic emission spectroscopy. The local structure of the film depends on the growth conditions and substrate temperature. TEM reveals a slight distortion of the film possibly leading to a breakdown of the symmetry from orthorhombic to monoclinic. At the highest growth temperatures, a well-defined interface is observed within the LCMO film, parallel to the substrate surface; this interface divides the film into two lamellae with a different microstructure. The one close to the substrate is perfectly coherent with the substrate, suggesting that it is strained as a result of the lattice parameter mismatch; the upper lamella shows a typical domain structure with unusual translation interfaces characterized by a displacement vector of the type $\frac{1}{2}[101{]}_o$ and $\frac{1}{2}[101{]}_o$ when referred to the orthorhombic lattice.