Non-uniform oxygen diffusion in epitaxial La_0.7Sr_0.3MnO_3−δ film on SrTiO₃ substrate

The diffusion mechanism of oxygen transport in the epitaxial La_0.7Sr_0.3MnO_3−δ films was examined for different practically significant conditions of annealing. An indirect method based on the interrelation between the phase transition temperature and the oxygen index was used for stepwise monitoring of the oxygen content in the film. Using a serial procedure of film annealing at different temperatures, we have revealed the abnormal behavior of diffusion transport of oxygen. The analysis of experimental data using numerical simulations demonstrates non-uniformity of the diffusion coefficient across the film thickness. The nature of the spatial dependence of the diffusion coefficient is associated with the lattice distortions of the film material. (paper)