Infrared optical properties of La0.7Ca0.3MnO3 epitaxial films

The reflectance of La0.7Ca0.3MnO3 epitaxial thin films on perovskite substrates with a range of lattice constants is studied in the frequency range 50–5000 cm−1. The complex dielectric functions of the bare La0.7Ca0.3MnO3 films are obtained by modeling the measured reflectivity spectra of the two-layer La0.7Ca0.3MnO3/substrate system with separately measured dielectric functions of the bare substrate. The results thus derived indicate that the internal optical phonon modes of the MnO6 octahedra are strongly affected by the substrate-induced lattice distortion.