Tuning of anisotropy in Bi-based high temperature superconducting thin films

Abstract

• Highly anisotropic Bi-based superconducting thin films. • Development of planar defects in thin films enhance vortex pinning. • Pb substitution strengthen 2D pancake arrangement of vortices in CuO planes. • Origin of anisotropy influence the axial dependence of pinning potential. The origin of the anisotropy behavior in the thin films of Bi 1.75 Pb 0.25 Sr 2 Ca 2 Cu 3 O 10±δ grown using pulsed laser deposition technique on three single crystalline substrates was investigated using magnetotransport measurements. Based on the evolution of the activation energy deduced from the magnetotransport data, it is surmised that Pb substitution in the present system strengthens the two-dimensional pancake arrangement of the vortices in the superconducting slab, which enhances the pinning of the vortices to the defect sites. The development of these planar defects with the decrease in the dimensionality of the sample was found to be the reason for the enhanced value of the pinning potential obtained in the thin film samples compared to the bulk. The interplay of Pb-assisted cation chemistry was found to have an influence on the anisotropy behavior in these films leading to an axial dependence of the pinning potential. Film grown on SrTiO 3 substrate with an anisotropy factor of ∼ 26 and higher superconducting parameters is the most anisotropic among the series of samples investigated.