Excess conductivity and magnetoresistance analysis for (BSF)x/(Bi, Pb)-2223 composite

Abstract This study examined the impact of adding hard ferrite Ba 0.5 Sr 0.5 Fe 12 O 19 (BSF) nanoparticles to the Bi 1.8 Pb 0.4 Sr 2 Ca 2 Cu 3.2 O 10+δ (Bi, Pb)-2223) superconductor phase. The investigation specifically focused on evaluating the critical current density, fluctuation-induced conductivity, and magnetoresistance of nano-(BSF) x /(Bi, Pb)-2223 composite, where 0.00 ≤ x ≤ 0.20 wt.%. The results revealed that the critical current density, J c , increased with the addition of nano-(BSF) up to x = 0.04 wt.%, reaching a value of 441.20 A/cm 2 . The Aslamazov and Larkin (A–L) approach has been evaluated the fluctuation-induced conductivity. Several superconducting parameters, including coherence length ζ c (0), effective layer thickness d , penetration depth λ pd (0), and Fermi energy $${E}_{F}$$ E F showed improvement as the concentration of nano-(BSF) increased up to x = 0.04 wt.%. In addition to Ginzburg–Landau critical parameters, such as the thermodynamic critical field B c (0), lower critical magnetic field B c1 (0), upper critical magnetic field B c2 (0), and critical current density J c (0) demonstrated an increase up to x = 0.04 wt.%, followed by a decrease for higher concentrations. The magnetoresistance measurements were performed at various applied DC magnetic fields, with values ranging from 0.29 to 4.44 kG, and were analyzed using the thermally activated flux creep (TAFC) and Ambegaokar–Halperin (AH) models. The calculated flux pinning energy ( U ) increased with the addition of nano-(BSF) up to x = 0.04 wt.% and then decreased for x > 0.04 wt.%. Furthermore, the transition width (Δ T ), was observed to increase as the applied magnetic field values increased. Moreover, the addition of nano-(BSF) increased the field-independent critical current density, J c,0 (0), up to x = 0.04 wt.%, after which it decreased for higher concentrations.