Scanning Hall probe measurements of field distributions of a coated conductor underapplied fields

Abstract

We measured the field profiles near the surface of a coated conductor (CC) under variousapplied fields by using the scanning Hall probe method. The field, applied inthe normal direction, was increased from zero to 171.5 Oe and then decreased to−58.8 Oe. We could not analyse our data completely by the direct use of Brandt’s calculation butby a modification with unusual field dependences of the introduced parameters.Since Brandt’s original calculation was based on homogeneous films, it was notsuitable for CCs with coarse granular structures. The modified calculations withappropriate parameters are related to the coarse granular structures. Those parameters,D,Jc,and R, represent the three characteristics of the flux penetration network: the averagedistance of flux penetrations, the density of critical sheet currents, and the range ofmeandering of the flux penetration front, respectively. The external field dependences ofthese parameters were different from those of the classical critical state model.