Electronic structure and phase separation in LaxMnO3 films (0.83≤x≤1.10): Optical and magnetooptical data

Abstract

The variations in the electronic structure and the evolution of phase separation as a result of creation of vacancies or excess of lanthanum in lanthanum manganites are studied on the basis of analysis of optical and magnetic properties of LaxMnO3 epitaxial films (0.83≤x≤1.10) in the fundamental absorption range. The Kerr effect, the temperature dependences of resistivity, optical density, and magnetoabsorption of light indicate the charge and magnetic phase separation in the films. The fine structure observed in the spectrum is attributed to spectral overlapping of electron transitions with charge transfer and geometrical resonances reflecting an inhomogeneous nanoscopic structure of the films, which strongly depends on stoichiometry and stresses emerging during film deposition. It is shown that, in contrast to bulk polycrystals, the gradient of stresses over the film thickness significantly affects the phase separation in the films.