Pressure-temperature phase diagram of charge ordering in Nd1/2Sr1/2MnO3

We observe how the charge-ordering (CO) temperature TCO of Nd1/2Sr1/2MnO3 decreases with the external pressure p from 160K at p=0 down to 30K at p? 4.5GPa, by measuring the values p, T where the far-infrared spectral weight of the metallic phase is fully recovered. We thus determine the (p, T) phase diagram of CO in that manganite. We also find that the parameter d(lnTCO)/dp which describes this metallization from the CO phase is equal and opposite to the quantity d(lnTc)/dp which governs the metallization of the paramagnetic state at comparable Curie temperatures Tc, in similar manganites at half-doping.