Magnetization and Magneto-resistance in Y(Ba1-xSrx)2Cu3O7-{\delta} (x = 0.00 - 0.50) superconductor

Here we present the magnetic properties and upper critical field (BC2) of polycrystalline Y(Ba1-xSrx)2Cu3O7-{\delta} superconductors, which are being determined through detailed ac/dc susceptibility and resistivity under magnetic field (RTH) study. All the samples are synthesized through solid state reaction route. Reduction in Meissner fraction (the ratio of field cooled to zero field cooled magnetization) is observed with increasing Sr content, suggesting occurrence of flux pining in the doped samples. The ac susceptibility and resistivity measurements reveal improved grain couplings in Sr substituted samples. Consequently the inter-grain critical current density (Jc), upturn curvature near the Tc in temperature dependence of upper critical field [BC2(T)], and BC2 are enhanced. Both Jc and BC2 increase in lower Sr substitution (up to x = 0.10) samples followed by decrease in higher doping due to degradation in effective pining and grain coupling.Comment: 17 pages text + Figs, [email protected]

Superconducting and Magnetic Properties of Zn-doped YBa2 Cu3 O7−δ

The superconducting properties and AC/DC magnetic properties of YBa2 Cu3−x Znx O7−δ , (x = 0.0, 0.01,0.03, 0.05, 0.10 and 0.15) compounds were investigated. Samples were synthesized through solid-state reaction route. X-ray diffraction data confirms the single-phase orthorhom- bic/tetragonal crystallization for the studied samples. Thermo-Gravimetric Analysis (TGA) was done for pure and Zn-doped YBa2 Cu3 O7−δ (YBCO) samples. Results re- veal that at higher dopant levels the doped samples are more oxygen-deficient than the undoped ones. The super- conducting properties of YBa2 Cu3−x Znx O7−δ system al- ways enhance with addition of oxygen to Cu–O chains, which causes enhancement of superconducting carrier den- sity together with orthorhombic structure. Zn substitution causes an overall reduction of superconducting condensa- tion energy with systematic degradation of superconduct- ing properties like Tc and Jc . This occurs via induced non- homogeneity of hole carrier density created by extended na- ture of perturbation on electronic structure in CuO2 planes and its weak-link type behavior. AC susceptibility measure- ment reveals that Zn doping reduces the inter-granular cou- plings. Scanning Electron Microscope (SEM) images indi- cate that increment of average grain size with increasing of Zn concentration

High field magneto-transport and magnetization study of Y1-xCaxBa2Cu3O7-delta (x=0.00-0.25)

We report DC isothermal magnetization, global critical current density (J(C)), Intra-grain critical current density (J(c)(intra)) and resistive upper critical field (B-c2) of polycrystalline Y1-xCaxBa2Cu3O7-delta (YBCO); x = 0.00, 0.05, 0.10, 0.15, 0.20 and 0.25. Ca doping at Y sites in YBCO superconductor results in flux pinning property, which can enhance the critical current densities and upper critical fields. J(C) and J(c)(intra) are experimentally calculated through DC isothermal magnetization measurement (M-H), employing the well known Bean's critical model. It is observed that both type of current densities (global and intra) enhance in lower doped (5%) samples and can be accounted in terms of reaching maximum of pinning centers and improved grain couplings nature. The upper critical field (B-c2) increases with Ca content being consistent with enhanced grain coupling nature of doped samples