Effect of strain on the local perovskite structure: La0.5Sr0.5CoO3

Extended x-ray-absorption fine structure has been used to study the bond-length and bond-angle distortions in thin (∼220 Å) La0.5Sr0.5CoO3 films grown epitaxially on SrTiO3 and LaAlO3 substrates. Growth on these substrates produces films with both in-plane tensile and in-plane compressive strains, respectively. It is found that the strain imposed on the thin-film lattice is accommodated mostly through changes in the first-shell Co–O bond lengths and third-shell Co–Co distances, while second-shell Co–La and Co–Sr distances behave similarly to distortions found previously in the tetrahedral semiconductors; i.e., they are most strongly affected by bond-angle distortions that account for the relaxation of the film lattice constant perpendicular to the film/substrate interface. These structural changes are directly correlated with the magnetic properties of the films.