Ferromagnetic artificial pinning centers in superconducting Nb0.36Ti0.64 wires

Abstract

We used ferromagnetic artificial pinning centers in superconducting NbTi wires to achieve a large critical current density (Jc) in a magnetic field. Four wires were fabricated that contained nanometer-sized arrays of Ni or Fe pins inside micron-sized filaments of Nb0.36Ti0.64 alloy. A ferromagnetic pin volume of only 2% Ni produced Jc’s (e.g., 2500 A/mm2 at 5 T, 4.2 K) that were comparable to those of commercial wires that have a pin volume of ∼20% Ti. We conclude that ferromagnetic artificial pins are more effective than nonmagnetic pins for a given volume percent.