Measurement and modeling of macroscopic ferromagnetic/high-Tc superconductor hybrid structures: applications to drilled bulk HTS with ferromagnetic materials inserted inside the holes.

Hybrid ferromagnetic/high-Tc superconductors (F/S) structures are realized by inserting iron cylinders inside the macroscopic columnar holes of drilled bulk high-Tc superconductors. The ferromagnetic material, with its tendency to concentrate the magnetic flux lines, modifies the magnetic properties of HTS that are characterized by a repulsion of the flux lines. In particular, the trapped field distribution of hybrid F/S results from a trade-off between the opposite magnetic properties of both materials. With the help of a 3-axis Hall probe mapping experiment, we characterize both vertical and transverse components of the trapped magnetic field. The distribution of the magnetic field trapped in the neighborhood of a hole inside which a ferromagnetic material is inserted is further investigated by high-resolution magneto-optic images. Experimental results are discussed with the help of a 3D finite-element model of hybrid F/S structure