Nanoscale phase separation in La0.7Ca0.3MnO3 films: evidence for texture-driven optical anisotropy

The infrared optical absorption (0.1 eV < ℏω < 1.5 eV) in La0.7Ca0.3MnO3 films on LaAlO3 substrates exhibits a drastic temperature evolution of the spectral weight, evidencing an insulator-to-metal transition. Single-crystal films were found to reveal strong linear dichroism with anomalous spectral oscillations and fairly weak temperature dependence. Starting from the concept of phase separation, we develop an effective medium model to account for these effects. The optical anisotropy of the films is attributed to the texturization of the ellipsoidal inclusions of the quasimetal phase caused by a mismatch of the film and substrate and the twin texture of the latter.