Comparative study of ferromagnetic and anti -ferromagnetic nanoparticles as artificial flux pinning centers in CuTl-1223 superconductor

The role of magnetically different nanoparticles (i.e. Cr, Ni and Co) as artificial flux pinning agents added in (Cu0.5Tl0.5)Ba2Ca2Cu3O10-(delta) (CuTl-1223) superconducting matrix was comparatively explored. (M-x)-(CuTl-1223); {M = Cr, Ni and Co; x = 0 and 1.0 wt%} nanoparticles-superconductor composites were synthesized by solid-state reaction (ceramic method) and their infield (magnetic) superconducting properties were investigated. The flux pinning strength of host CuTl-1223 superconducting matrix was enhanced with the addition of anti-ferromagnetic Cr nanoparticles, while was suppressed with the addition of ferromagnetic (Ni and Co) nanoparticles. The enhancement and suppression in flux flow activation energy with addition of anti ferromagnetic (Cr) and ferromagnetic (Ni and Co) nanoparticles were observed respectively. The ferromagnetic (Ni and Co) nanoparticles at grain-boundaries get magnetized in the direction of applied magnetic field due to which a repulsive force is generated between pinning site (inter-granular site) and flux vortex that results in enhanced vortex dynamics within the grain surrounded by grain-boundaries. The net magnetization of anti ferromagnetic Cr nanoparticles is zero, so these non-superconducting nanoparticles present at grain-boundaries do not show repulsion to magnetic vortex and serve as effective pinning centers.