Twinning in La1-xSrxMnO3 thin films, which grew coherently on (001)-oriented cubic substrates, was explained as a result of shear strain relaxation within the distorted rhombohedral crystal lattice. A one-dimensional periodic model structure for twins was proposed and the non-uniform elastic strains within the twinned films were calculated by using the coherency-defect technique. The strain field depended upon the ratio of the domain width to the film thickness and exhibited maxima at the triple junctions of the domain boundaries and the film/substrate interface. The equilibrium domain width was 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. By comparing the theoretical results with electron microscopic observations of twins, the domain-wall energy could be predicted. From the observed average domain width in La0.67Sr0.33MnO3 films, a domain-wall energy of 1.35mJ/m2 was deduced.

Modeling of Twinning in Epitaxial (001)-Oriented La0.67Sr0.33MnO3 Thin Films. N.Farag, M.Bobeth, W.Pompe, A.E.Romanov, J.S.Speck: Journal of Applied Physics, 2005, 97[11], 113516