FLUX-PINNING IN MULTIFILAMENTARY SUPERCONDUCTING WIRES WITH FERROMAGNETIC ARTIFICIAL PINNING CENTERS

We demonstrate that ferromagnets are effective artificial pinning cent ers for the enhancement of critical current (J(c)) in multifilamentary superconducting wires. We have analyzed theoretically the proximity e ffect due to the FM pins near the final size of several nanometers and determined that one should achieve a large pinning force by such cent ers at these sizes. There is also additional pinning strength resultin g from the interaction between ferromagnetic moments of the pins and t he magnetic field gradient of the fluxon lattice. The measured results of J(c), T-c and H-c2 are analyzed, and compared with our model analy sis.