Effect of magnetic nanoparticles on superconducting properties of YBCO. Comparative study of Y-123 and Y-358

      Аннотация: In this book, we have performed a comparative study between the two superconductors YBa2Cu3O7-y (Y-123) and Y3Ba5Cu8O18±y (Y-358) compounds. We have investigated the influence of magnetic nanoparticles CoFe2O4 addition on the structural, microstructural and electrical properties in both compounds. The obtained results reveal the existence of much more disorder in Y-358 compound due to a greater number of Cu sites to be substituted by Fe and Co compared to Y-123. Then we have analysed the effects of magnetic nanoparticles addition on the normal state resistivity of Y-123 and Y-358 samples. This investigation confirms the accentuated disorder in the Y-358 compound compared to Y-123 one. On the other hand, we have studied the excess of conductivity on the basis of the Aslamazov–Larkin theory in Y-123 and Y-358 samples added with various amount of CoFe2O4. Superconducting parameters are affected by the nanoparticles addition and results are discussed in relevance to the structural and microstructure differences between Y-123 and Y-358. It appears that this comparative study makes it possible to distinguish without ambiguity between the Y-123 and Y-358 superconductor compounds.

Ключевые слова: Excess conductivity, Superconductors, Electrical normal state resistivity, flux pinning, Magnetic nano-particles