FERROMAGNETIC ARTIFICIAL PINNING CENTERS IN SUPERCONDUCTING NB0.36TI0.64 WIRES

We used ferromagnetic artificial pinning centers in superconducting Nb Ti wires to achieve a large critical current density (J(c)) in a magne tic field. Four wires were fabricated that contained nanometer-sized a rrays of Ni or Fe pins inside micron-sized filaments of Nb0.36Ti0.64 a lloy. A ferromagnetic pin volume of only 2% Ni produced J(c)'s (e.g., 2500 A/mm(2) at 5 T, 4.2 K) that were comparable to those of commercia l wires that have a pin volume of similar to 20% Ti. We conclude that ferromagnetic artificial pins are more effective than nonmagnetic pins for a given volume percent. (C) 1996 American Institute of Physics.