Electromagnetics of Superconductor/Paramagnet Heterostructures

Abstract Redistribution of the transport current in a superconductor affected by paramagnetic shields provides a possibility of strongly overcritical states and a drastic reduction of AC losses in thin superconductor films and tubes. Such superconductors subject to para- or diamagnetic shielding are studied by means of the potential theory and the critical state model when carrying a transport current or exposed to an external magnetic field. Analytical results are obtained for a number of shielding geometries and confirmed by numerical solutions. It is shown that using magnetostatic-electrostatic analogies allows consideration of paramagnetic shielding configurations of arbitrary shapes and magnetic permeabilities by means of common finite-element solvers to enhance the dissipation-free transport currents in superconductors and reduce AC losses in them. Furthermore, using the generalized London theory, the penetration of magnetic flux into magnetically shielded bulk superconductors is studied and the enhancement of the Bean-Livingston barrier is established.