High-pressure far-infrared absorption measurements on La1−xCaxMnO3−δ by means of synchrotron radiation

High-pressure far-infrared absorption measurements carried on three La1−xCaxMnO3−δ samples, exploiting synchrotron radiation are reported. Present data represent the first measurement of this kind performed on manganites. Our results show a pressure-induced charge delocalization effect only in the stoichiometric samples, whereas a complete metallization is not achieved. The pressure dependence of the frequencies of the main phonon bands and of the gap-energy is presented and discussed. An interpretation of our results in terms of a phase separation scenario is also proposed.