Determination of relative pinning strength of hexagonally arranged composite pinning centers

摘要

A method to determine the relative pinning strength of different pinning sites in composite hexagonal pinning arrays is proposed and experimentally realized. Six different samples of superconducting Nb films with composite hexagonal arrays were fabricated and measured. Two types of pinning sites have different sizes. The density of one type of pinning site is twice that of the other. The critical current versus the applied magnetic fields were also measured. The vortex configurations at the matching fields can be deduced from these curves and verified by molecular dynamic simulations. The relative pinning strength of different pinning sites can be determined from these configurations. The method could be extended to decide the optimal pinning size or to compare the pinning strength of pinning sites made of different materials.