Dimensionality Fluctuation in the Superconducting Order Parameter of YBa_2Cu_3O_(7-δ+x) CoFe_2O_4 Composite

摘要

Fluctuations on the electrical conductivity of polycrystalline YBa_2Cu_3O_(7-δ) + x CoFe_2O_4 (x = 0.0,0.1,0.2, and 0.3 wt.%) superconductors were investigated from the resistivity vs. temperature data. Attempts have been made to identify the optimum inclusion of ferromagnetic CoFe_2O_4 particles in YBa_2Cu_3O_(7-δ) (YBCO) superconductor. With the increase of CoFe_2O_4, T_c decreases and dropped sharply with higher wt.%. Excess conductivity fluctuation analysis using Aslamazov-Larkin (AL) model fitting reveals transition of two dominant regions (2D and 3D) above T_c. The decrease in 2D-3D crossover temperature (Lawerence-Doniach temperature) in the mean field region has been observed as a consequent dominance of 3D region with increase in wt.% of CoFe_2O_4 in the composite.