Magnetic field dependent critical current density of Bi–Sr–Ca–Cu–O superconductor in bulk and tape form with addition of Fe3O4 magnetic nanoparticles

Abstract

The (Bi,Pb)2Sr2Ca2Cu3O10-(Fe3O4)x superconductor for x=0, 0.01, 0.03, and 0.05 were prepared. The average size of Fe3O4 used was 40 nm. The maximum critical current density (Jc) in the bulk form was observed in the x=0.01 sample. Based on this result, Ag sheathed high temperature superconductor tapes with starting compositions (Bi,Pb)2Sr2Ca2Cu3O10-(Fe3O4)0.01 were fabricated using the powder in tube method. The microstructure, phase formation, critical temperature, and transport critical current density were studied. The Jc of the nanosized Fe3O4 added tapes is 5130 A/cm2 at 77 K and 23130 A/cm2 at 30 K in zero fields. The nonadded tapes showed a lower Jc, 3090 A/cm2 at 77 K and 12 400 A/cm2 at 30 K. A sudden decrease in Jc in low magnetic fields (B<0.10 T) when applied parallel and perpendicular to the tapes surface was observed. By adding magnetic nanoparticles, the full vortex magnetic energy can be used to enhance Jc and thus, magnetic nanoparticles such as Fe3O4 can act as an effective flux pinning center leading to the enhancement of Jc in the bulk as well as the tape form.