HREM and XRD characterization of epitaxial perovskite manganites

Thin films of the perovskite manganites solid solutions, including (La, R)( 1-x)A(x)MnO(3) (R = Pr, Nd, A = Ca, Sr, Na) on the single crystalline subst rates (LaAlO3, SrTiO3, ZrO2(Y2O3), MgO) were characterized by X-ray diffrac tion and HREM. Some compounds (like (La1-xPrx)(0.7)Ca0.3MnO3) have an ortho rhombic structure while others (like La1-xNaxMnO3 and La0.7Sr0.3MnO3) are r hombohedral. A strong tetragonal lattice strain owing to the film-substrate lattice mismatch was found in particular in very thin films. In the thicke r films this strain was more persistent for compositions the bulk of which is orthorhombic. By HREM, twinning due to the cubic to orthorhombic phase t ransition was found for (La1-xPrx)(0.7)Ca-0.3 MnO3 films, whereas XRD gave the mean tetragonal ratio of the lattice parameters. Misfit dislocations wi th various Burger vectors occur in the manganites films on LaAlO3 and SrTiO 3. An example of the growth of the epitaxial heterostructures with CMR mang anites and high T-c superconductors is given. (C) 2000 Elsevier Science B.V . All rights reserved.