Anisotropic in-plane reversible strain effect inY0.5Gd0.5Ba2Cu3O7 − δ coated conductors**Contribution of NIST, not subject to US copyright.

Abstract

Recent experiments have shown that reversible effects of strain on the criticalcurrent density and flux pinning strength in the high-temperature superconductorBi2Sr2Ca2Cu3Ox can beexplained entirely by the pressure dependence of its critical temperature. Such a correlation is less simplefor RE–Ba2Cu3O7 − δ (RE = rare earth) superconductors, in part because the in-plane pressure dependence of its critical temperatureis highly anisotropic. Here, we make a qualitative correlation between the uniaxial pressuredependence of the critical temperature and the reversible strain effect on the critical current of RE–Ba2Cu3O7 − δ coated conductors by taking the crystallography and texture of the superconducting filminto account. The strain sensitivity of the critical current is highest when strain is orientedalong the [100] and [010] directions of the superconducting film, whereas the criticalcurrent becomes almost independent of strain when strain is oriented along the[110] direction. The results confirm the important role of the anisotropic pressuredependence of the critical temperature on the reversible strain behavior of RE–Ba2Cu3O7 − δ. The reversiblestrain effect in RE–Ba2Cu3O7 − δ is expected to decrease the performance of the conductor in many applications, such ashigh-field magnets, but the effect may be only minor in coated conductor cables, wherestrain is generally not aligned with the tape axis.