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Growth and superconducting properties of Bi2Sr2CaCu2O8 + δ thin films incorporated with iridate nanoparticles



Iridate nanoparticle AIrO3 (A = Sr, Ba) incorporated Bi2Sr2CaCu2O8 + δ (Bi-2212) thin films were successfully grown using pulsed laser deposition with post-growth ex situ heat treatment. Nanosized particles of SrIrO3 (Sr-iridate) and BaIrO3 (Ba-iridate) were deposited on top of MgO (100) substrate, followed by Bi-2212 layers to investigate their effects on the physical and superconducting properties of Bi-2212 thin films. The number of laser pulses was changed from 450 to 1800 to control the density of iridates in the Bi-2212 matrix. The composite film is then partial-melted at 890 °C for 15 min and annealed at 850°C for 5 h in ambient air. Scanning electron microscopy shows that the surfaces of thin films with iridates are more compact with minimal voids and porosity than those of pure Bi-2212 thin films. Both types of iridate incorporation suppress Tc-zero of Bi-2212 thin films. Incorporating Sr-iridate in the Bi-2212 strongly affects Tc-zero than those with Ba-iridate at low density. However, both iridate incorporations result in the expansion of the c-axis lattice constant and variation of Bi/Sr ratio of Bi-2212 films. On the other hand, we observed improvement of the activation energy, U0, as well as the self-field critical current density, Jc(0), of Bi-2212 films with incorporated iridates even with suppressed Tc-zero.