Critical Current and Pinning Effect in Type I Superconducting Lead Foils with Thickness Modulation

抄録

By shadow electron microscopy, the critical current density J_p has been measured in lead foils with a periodic one-dimensional thickness modulation. The superconducting and normal laminae in the intermediate state are produced to be parallel to the grooves on the specimen surface. The J_p in the modulated-surface specimen is larger than that in the flat-surface specimen. The enhancement of J_p as a function of temperature shows anomalies at some temperatures where abrupt changes of the laminar structure are observed. These anomalies are attributed to the discontinuous changes of the period of the laminar structure due to redistributions, but not to the increment of the number of the effective pinning centers due to the matching effect.