Pressure dependence of Tc in NdBa2Cu3O7- delta to 6 GPa.

The superconducting transition temperature T c for NdBa 2 Cu 3 O 7-δ is measured as a function of pressure to 6 GPa. The pressure applied to these materials is directly measured near T c , which is determined by monitoring the ac susceptibility as a function of temperature. It has been suggested that the apparent absence of superconductivity in PrBa 2 Cu 3 O 7-δ is due, at least in part, to the interaction of 4f electrons of Pr 3+ with the Cu-O plane