Flux Pinning Property of Artificially Introduced Nb in Nb-Ti Superconductors
The elementary pinning force of thin Nb layers introduced as artificial pinning centers in Nb-Ti is theoretically investigated in the relatively low field region using the Ginzburg-Landau theory. It is found that the pinning energy comes from the kinetic energy due to the induced superconductivity in the Nb layers by the proximity effect. Hence, these layers act as repulsive pinning centers, while normal layers such as α-Ti do as attractive ones. The elementary pinning force depends sensitively on the coherence length in the Nb layers and is larger for the longer coherence length. This value is predicted to be larger than that of α-Ti layers in commercial Nb-Ti wires even in the case of short coherence length.
KeywordsCritical Current Density Coherence Length Critical Field Proximity Effect Normal Core
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