Role of anti-ferromagnetic Cr nanoparticles in CuTl-1223 superconducting matrix

• Superconductivity of CuTl-1223 matrix was suppressed after inclusion of Cr nanoparticles.
• Addition of Cr nanoparticles has not affected the crystal structure of CuTl-1223 phase.
• Diamagnetic signal of CuTl-1223 phase was decreased after addition of Cr nanoparticles.
• Suppression of superconductivity after addition of Cr nanoparticles was explained theoretically.

Anti-ferromagnetic chromium (Cr) nanoparticles were added to Cu0.5Tl0.5Ba2Ca2Cu3O10−δ (CuTl-1223) superconducting matrix to synthesize (Cr)x/CuTl-1223 (x = 0, 0.5, 0.75, and 1.0 wt.%) nano-superconductor composites. Different experimental techniques were used to study the structural, morphological, compositional and superconducting transport properties of these composites. It was observed that the addition of Cr nanoparticles had not altered the crystal structure of the host CuTl-1223 superconducting matrix, which indicates the presence of these nanoparticles at the grain-boundaries. Suppression of superconducting transport properties can be attributed to two factors (i) spins scattering by net magnetization due to uncompensated spins on the surface of these anti-ferromagnetic Cr nanoparticles and (ii) oxygen imbalance due to formation of Cr2O3 surface layers on these nanoparticles. The prominent reduction in the diamagnetic signal was also observed, which had indicated the decrease of superconducting volume fraction after the inclusion of Cr nanoparticles in the composites. Superconducting microscopic parameters such as coherence length {ξc(0)}, inter-layer coupling (J), Fermi velocity (VF) and Fermi energy (EF) of the carriers were determined as a function of Cr content in (Cr)x/CuTl-1223 nano-superconductor composites by excess conductivity analyses in three dimensional (3D), two dimensional (2D) and short wave dimensional (0D) fluctuation regions.

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