Effect of Ferromagnetic Induced Inhomogeneity in Excess Conductivity of YBa2Cu3O7-δ+x CoFe2O4 Composite

Abstract

Dimensional fluctuations of superconducting order parameters in YBa2Cu3O7- δ+ x CoFe2O4 (x = 0.0, 0.1, 0.2, and 0.3 wt%) has been analyzed. SEM micro-graphs reveal the reduced grain size with the incorporation of ferromagnetic CoFe2O4 particles in the YBCO matrix. With the increase of CoFe2O4 wt% it is found that the superconducting transition temperatures (Tc) determined from standard four-probe method decreases and dropped sharply with higher wt.% addition of CoFe2O4. Excess conductivity fluctuation analysis using Aslamazov-Larkin (AL) model fitting reveals transition of two dominant regions (2D and 3D) above Tc. 2D to 3D crossover temperature i.e. Lawerence-Doniach temperature (TLD) that demarcates dimensional nature of fluctuation inside the grains is influenced by CoFe2O4 incorporation in YBCO matrix. The decrease in TLD in the mean field region has been observed as a consequent dominance of 3D region with increase in wt% of CoFe2O4 in the composite. The decrease in zero-resistance critical temperature (Tc0) and increase in transition width (ΔT) signifies the degradation of inter-grain weak links.