Effect of strain, magnetic field and field angle on the critical current density of YBa2Cu3O7-δ coated conductors

A large, magnetic-field-dependent, reversible reduction in critical current density with axial strain in YBa2Cu3O7-delta coated conductors at 75.9 K has been measured. This effect may have important implications for the performance of YBa2Cu3O7-delta coated conductors in applications where the conductor experiences large stresses in the presence of a magnetic field. Previous studies have been performed only under tensile strain and could provide only a limited understanding of the in-field strain effect. We now have constructed a device for measuring the critical current density as a function of axial compressive and tensile strain and applied magnetic field as well as magnetic field angle, in order to determine the magnitude of this effect and to create a better understanding of its origin. The reversible reduction in critical current density with strain becomes larger with increasing magnetic field at all field angles. At 76 K the critical current density is reduced by about 30% at -0.5% strain when a magnetic field of 5 T is applied parallel to the c-axis of the conductor or 8 T is applied in the ab-plane, compared to a reduction of only 13% in self-field. Differences in the strain response of the critical current density at various magnetic field angles indicate that the pinning mechanisms in YBa2Cu3O7-delta coated conductors are uniquely affected by strain.