High-frequency conductivity and phonon properties of La7/8Sr1/8MnO3

We report on broadband frequency-dependent conductivity experiments on La7/ 8Sr1/8MnO3 that cover the frequency range from 0.3 meV (approximate to3 cm( -1)) to 5 eV (approximate to4 X 10(4) cm(-1)). At all frequencies investiga ted, the temperature dependence of sigma'(nu) reflects the structural and m agnetic phase transitions. At low frequencies we find the typical character istics of hopping conduction. The optical conductivity at frequencies above the phonon modes reveals strong changes at the structural and magnetic pha se transitions and can best be described in terms of polaronic conduction. In addition, we carefully analyzed the temperature dependence of the phonon modes. Distinct anomalies in the eigenfrequencies and the appearance of si de bands signal structural phase transitions.