Effects of strain relaxation in Pr_0.67Sr_0.33MnO₃ films probed by polarization dependent X-ray absorption near edge structure

摘要

The Mn K edge X-ray absorption near edge structure (XANES) of Pr_0.67Sr_0.33MnO₃ films with different thicknesses on (001) LaAlO₃ substrate was measured, and the effects of strain relaxation on film properties were investigated. The films showed in-plane compressive and out-of-plane tensile strains. Strain relaxation occurred with increasing film thickness, affecting both lattice constant and MnO₆ octahedral rotation. In polarization dependent XANES measurements using in-plane (parallel) and out-of-plane (perpendicular) geometries, the different values of absorption resonance energy E _r confirmed the film anisotropy. The values of E _r along these two directions shifted towards each other with increasing film thickness. Correlating with X-ray diffraction (XRD) results it is suggested that the strain relaxation decreased the local anisotropy and corresponding probability of electronic charge transfer between Mn 3 d and O 2 p orbitals along the in-plane and out-of-plane directions. The XANES results were used to explain the film-thickness dependent magnetic and transport properties.