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Abstract
We have obtained the three uniaxial-pressure derivatives of the critical temperature, ${\mathit{T}}_{\mathit{c}}$, for ${\mathrm{GdBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\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 ${\mathit{T}}_{\mathit{c}}$ when compressing across (along) the CuO chains. A comparison of the results in c-oriented R${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ films and superlattices for various R and substrates reveals a nonmonotonic relation between the critical temperature and pressure.
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