UNIAXIAL PRESSURE-DEPENDENCE OF THE SUPERCONDUCTING CRITICAL-TEMPERATURE IN RBA2CU3O7-DELTA HIGH-TC OXIDES

We have obtained the three uniaxial-pressure derivatives of the critical temperature, T(c), for GdBa2Cu3O7-delta from the hydrostatic pressure dependence measured on films of different crystalline orientations. The strain derivatives are found to be extremely anisotropic in the a-b plane, inducing a decrease (increase) of T(c) when compressing across (along) the CuO chains. A comparison of the results in c-oriented RBa2Cu3O7-delta films and superlattices for various R and substrates reveals a non-monotonic relation between the critical temperature and pressure.