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

Abstract The role of magnetically different nanoparticles (i.e. Cr, Ni and Co) as artificial flux pinning agents added in (Cu 0.5 Tl 0.5 )Ba 2 Ca 2 Cu 3 O 10 −δ (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.