Pressure dependence of ${\mathit{T}}_{\mathit{c}}$ in ${\mathrm{NdBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ to 6 GPa

The superconducting transition temperature ${\mathit{T}}_{\mathit{c}}$ for ${\mathrm{NdBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ is measured as a function of pressure to 6 GPa. The pressure applied to these materials is directly measured near ${\mathit{T}}_{\mathit{c}}$, which is determined by monitoring the ac susceptibility as a function of temperature. It has been suggested that the apparent absence of superconductivity in ${\mathrm{PrBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ is due, at least in part, to the interaction of 4f electrons of ${\mathrm{Pr}}^{3+}$ with the Cu-O plane. In light of this speculation, applying pressure to ${\mathrm{NdBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ might be expected to increase the interaction of 4f electrons of ${\mathrm{Nd}}^{3+}$ with electrons in the Cu-O plane and reduce ${\mathit{T}}_{\mathit{c}}$. Our results indicate that ${\mathit{T}}_{\mathit{c}}$ increases with applied pressure.