UC Irvine

We have determined the effect of pressure P on the resistance and superconducting transition temperature Tc of RBa2Cu3Ox (R=Gd,Er,andYb) and compare our results to those obtained on high-quality YBa2Cu3Ox. The transition temperature, which is 90 K or greater at ambient pressure for all four compounds, is enhanced by pressure in each at rates between 0.09 and 0.19 K/kbar. Interestingly, the presence of a localized moment in the rare-earth compounds appears to have no influence on the pressure response. From the positive dTcdP we infer a positive change in the thermal expansion upon entering the superconducting state. © 1987 The American Physical Society.