Pressure-induced charge delocalization in manganites studied by means of infrared spectroscopy.

Infrared absorption spectra of the La0.75Ca0.25MnO3 manganite have been collected over the spectral range 600-1100 cm-1 along isobaric paths at P 1/4 0,2,4, and 7 GPa in the 240-320 K temperature range. The pressure dependence of the insulator-to-metal transition temperature TIM has been determined from the spectra analysis and the first PT phase diagram of a manganite in the high-pressure regime is presented and discussed.