Studies on the proximity effect in Bi-based high-temperature superconductor/manganite heterostructures

The effect of proximity of the magnetism of the Pr-based manganite (Pr0.6Sr0.4MnO3) on the superconductivity of Bi-based high-temperature superconductor (Bi1.75Pb0.25Sr2Ca2Cu3O10+d) was studied based on the results obtained from the magnetotransport and magnetization measurements. Decrease in the values of the upper critical field (HC2(0)) and an increase in the width of the superconducting transition (Delta TC) of Bi1.75Pb0.25Sr2Ca2Cu3O10+d were observed in proximity with the manganite. The combined effect of magnetic exchange interaction arising from the manganite, the leakage of Cooper-pairs from the superconductor into the manganite, and the diffusion and transport of spin-polarized electrons from the manganite into the superconductor were found to modify the superconducting properties of Bi1.75Pb0.25Sr2Ca2Cu3O10+d. The stacking sequence of the individual layers in these heterostructures was found to dictate the ground state properties of the heterostructure. As a consequence of the proximity effect, the colossal-magnetoresistance (CMR) ratio as high as ~ 99 % observed in the heterostructure makes the thin film heterostructures promising candidates for potential technological applications.Comment: 29 pages, 14 figure

Evolution of Superconducting Properties of Coexistent Bi-2212 and Bi-2223 phases in BSCCO

391-397The evolution of superconducting properties of BSCCO superconductors, inadvertently hosting the two superconducting phases Bi-2212 and Bi-2223 have been investigated in pristine and Pb doped BSCCO. The superconducting transition temperature TC of Bi-2212 phase monotonically increases with increasing Bi-2223 phase fraction. On the other hand Bi-2223 phase exhibits depression in TC for its lower phase fractions (<24%) but attains its bulk value as Bi-2223 phase fraction is increased to 30%. This behavior has been rationalized by invoking the interplay of proximity effects between the two coexisting phases and establishment of Bi-2223 superconducting percolation path. In addition to aiding the formation of BSCCO with higher Bi-2223 phase fraction, the Pb substitution also leads to an enhancement of critical current density by the creation of pinning centres

Intricacies of Strain and Magnetic Field Induced Charge Order Melting in Pr0.5Ca0.5MnO3 Thin Films

Thin films of the half doped manganite Pr0.5Ca0.5MnO3 were grown on (100) oriented MgO substrates by pulsed laser deposition technique. In order to study the effect of strain on the magnetic field induced charge order melting, films of different thicknesses were prepared and their properties were studied by x-ray diffraction, electrical resistivity and magnetoresistance measurements. A field induced charge order melting is observed for films with very small thicknesses. The charge order transition temperature and the magnetic filed induced charge order melting are observed to depend on the nature of strain that is experienced by the film.Comment: 18 pages, (including 6 figures

Evolution of Superconducting Properties of Coexistent Bi-2212 and Bi-2223 phases in BSCCO

The evolution of superconducting properties of BSCCO superconductors, inadvertently hosting the two superconducting phases Bi-2212 and Bi-2223 have been investigated in pristine and Pb doped BSCCO. The superconducting transition temperature TC of Bi-2212 phase monotonically increases with increasing Bi-2223 phase fraction. On the other hand Bi-2223 phase exhibits depression in TC for its lower phase fractions (&lt;24%) but attains its bulk value as Bi-2223 phase fraction is increased to 30%. This behavior has been rationalized by invoking the interplay of proximity effects between the two coexisting phases and establishment of Bi-2223 superconducting percolation path. In addition to aiding the formation of BSCCO with higher Bi-2223 phase fraction, the Pb substitution also leads to an enhancement of critical current density by the creation of pinning centres