Magnetic shielding efficiency of superconducting/ferromagnetic systems

Abstract

We studied magnetic flux penetration in a hybrid MgB2/Fe structure consisting of two coaxial cups in a magnetic field applied parallel to their axis. This analysis was performed to investigate the potential of magnetic shielding of systems with a reduced length/radius aspect ratio exploiting the opposite magnetic properties of superconducting and ferromagnetic materials. We measured the field attenuation for applied magnetic fields up to 1.5 T, in different positions along the cup axis. At higher fields, the hybrid solution gives shielding factors up to more than three and four times higher than those of the MgB2 cup alone at T = 20 and 30 K, respectively. This improvement changes as a function of the applied field and of the position along the cup axis and cannot be explained as a straightforward composition of the independent shielding contributions of the ferromagnetic and superconducting layers.