Correlation between magnetism and "dark stripes" in strained La_1-xSr_xCoO₃ epitaxial films (0 ≤ x ≤ 0.1)

Using the technique of aberration-corrected scanning transmission electron microscopy, we performed a systematic analysis for the atomic lattice of the strained La_1-xSr_xCoO₃ (0 ≤ x ≤ 0.1) epitaxial films, which have drawn a great attention in recent years because of their anomalous magnetism. Superstructures characterized by dark stripes are observed in the lattice image, evolving with combined Sr-doping and lattice strains. Fascinatingly, we found a close relation between the proportion of the Co ions in dark stripes and the saturation magnetization of the film: the latter grows linearly with the former. This result implies that the magnetism could be exclusively ascribed to the Co ions in dark stripes.