Contactless measurements of local transport characteristics of coated conductors under the bending strain

The influences of bending strain on the critical current density J_c in coated conductor (CC) tapes were investigated at 77 K by contactless method based on scanning Hall probe magnetometry (SHPM). In order to clarify the reasons of variations in critical current for different bending radius we carried out local studies of critical currents in CC tapes before and after bending strain. By using SHPM we defined two-dimensional maps of critical current distribution at various bending radiuses. It was demonstrated that the superconducting layer in CC tape cracked at critical bending radius into periodical regions with unchanged and decreased transport properties. Appearance of local cracks with reduced value of the critical current leads to degradation of the critical current of the whole tape. It is found that the both critical bending radius and kind of tape cracking depend on the type of metallic substrates. The results of contactless studies are in good agreement with direct transport measurements.