Magnetic field effect on the electrical resistivity of Y1−xNixBa2Cu3O7−δ superconductor

Abstract The Ni- substituted Y 1−x Ni x Ba 2 Cu 3 O 7−δ high temperature superconducting samples with 0 ≤ x  T c 0 , (ρ = 0), under applied magnetic fields, weak links are affected and the vortices are penetrated and move inside the intergranular and then the tail part is broaden. This broadening part observed in the electrical resistivity, ρ( T ), and in the derivative of the electrical resistivity, dρ/d T , becomes too small or even absent in Ni doped samples. For pure sample, T c 0 was around 90 K; by applying a magnetic field H = 0.3 T it shifted to 40 K. This broadening is 91.4 K to 80 K for x = 0.002 and 91.7 K to 85 K for x = 0.004 samples. We found an optimal value of Ni doping concentration which improves the coupling of the grains. Then, vortices get strongly pinned. These observations suggest that the Ni substitution can reduce the weak links and increase the J c values of these superconductors.