Modeling of twinning in epitaxial (001)-oriented La0.67Sr0.33MnO3 thin films -: art. no. 113516

Twinning, i.e., the formation of structural domains, in La1-xSrxMnO3 thin films, which grow coherently on (001)-oriented cubic substrates, is explained as a result of shear strain relaxation within the distorted rhombohedral La1-xSrxMnO3 crystal lattice. A one-dimensional periodic model structure of twins is proposed and the nonuniform elastic strains within twinned La1-xSrxMnO3 films are calculated by applying the coherency-defect technique. The strain field depends on the ratio of the domain width and film thickness and exhibits maxima at the triple junctions of the domain boundaries and the film/substrate interface. The equilibrium domain width is derived as a function of the film thickness by minimizing the total energy of the system including contributions from elastic strain and domain-wall energy. From comparison of the theoretical results with recent electron microscope observations of twins the domain-wall energy can be predicted. From the observed average domain width in La0.67Sr0.33MnO3 films, the domain-wall energy of 1.35 mJ/m(2) is suggested. The possibility of a preferred nucleation of the ferromagnetic phase at triple junctions due to spatial strain variations is discussed. (C) 2005 American Institute of Physics.