Critical Current Density and Magnetic Phase Diagrams in Nb-Ti Superconducting Wires with Artificial Pinning Centers

Abstract

Critical current densities (J_c) due to artificially designed pinning structure composed of randomly oriented Nb/Nb-Ti or Ti/Nb-Ti multilayer clusters in Nb-Ti superconducting wires are investigated in terms of recent works on magnetic phase diagrams of the metallic superconducting multilayer system. Upper critical field (B_c2)-temperature curves of the Nb-Ti superconducting wires with artificial pinning structures have an anomalous upturn of B_c2. This behavior is similar to the dimensional crossover which occurs in the superconducting multilayer system. From J_c and anomalous B_c2 properties in the Nb-Ti superconducting wires with artificial pinning strutures, we propose the flux pinning mechanism of these systems, especially in the high field region at 4.2 K.