Suppression of ac (hysteretic) loss by magnetic shielding of MgB[sub 2]/Fe superconductors: The pseudo-Meissner effect

Improvement of critical current in MgB2/Fe superconducting wires by a ferromagnetic sheath

“…For higher fields, the shielding rapidly weakened and for H>0.4T the entire external field additional to 0.4T was passed t hrough the Fe sheath, i.e. H in 5 against H out was parallel to the data with no shield for H>0.4 T. These measurements are in good quantitative agreement with calorimetric measurements of ac loss in a similar MgB 2 /Fe wire 8 . However, the measured shielding is better than that given by the analytical expression for an infinite cylindrical shield of the same thickness and magnetic permeability 9 (solid line in Fig.3).…”

“…A model by Genenko et al 7 predicted either a suppression or enhancement of the loss-free transport current of a superconducting strip in magnetic surroundings. Earlier measurements 5,8 indicated the existence of magnetic shielding in MgB 2 /Fe tapes. In this paper, we present the first detailed measurements of the field dependence of transport J c , influenced by magnetic shielding and interaction between the Fe sheath and the superconductor in round MgB 2 /Fe wires.…”