Shear-strain-induced low symmetry phase and domain ordering in epitaxial La0.7Sr0.3MnO3 thin films

The domain structure in epitaxial La0.7Sr0.3MnO3 films grown on (LaAlO3)0.3(Sr2AlTaO6)0.7(001) substrates has been investigated by x-ray reciprocal space maps on (003), (103), (1¯03), (013), and (01¯3) reflections in the high-resolution scattering zone containing the c* axis, and the transmission electron microscopy. We revealed that at above 20nm, the films show clearly a low symmetry monoclinic phase, and the shear strain relaxation can induce a patterned domain structure and in-plane superlattice in the films. The domain width versus the film thickness and the shear strain effect on the Curie temperature of the films were also discussed.