Infrared study of charge delocalization induced by pressure in the La0.75Ca0.25MnO3 manganite - art. no. 184410

We measured the pressure dependence of the room-temperature infrared absorp tion spectrum of the pseudocubic La0.75Ca0.25MnO3 manganite. On increasing pressure up to 10 Gpa we observe the increase of a broad band associated wi th polaronic absorption, which partially screens the high-frequency phonon at high pressures. We also measured absorption spectra of the same sample a s a function of temperature, and of the layered Sr1.5La0.5MnO4 manganite as a function of pressure. The comparison between different sets of spectra c learly shows that the increase of the broad-band absorption observed in the La0.75Ca0.25MnO3 manganite is due to a pressure-induced charge delocalizat ion process. However, the metallic state is not achieved at room temperatur e, at least in the explored pressure range.