Bean-Livingston barrier and dynamics of the magnetic flux flow in layered (plated) superconductors

摘要

Magnetic flux flow in layered NbTi/Nb and textured superconducting ceramics Bi2Sr2CaCu2O8+d with the nearly reversible magnetization curve are measured. The characteristic time of the magnetic moment relaxation of such superconductors is determined by the viscous flux flow. It is observed, that in a parallel to superconducting layers external magnetic field the characteristic time of the magnetic flux inflow into the sample and the time of the flux outflow from the sample differ in several times. This difference in the characteristic times is unequivocally due to the flux flow into the sample through the end plates of the thin superconducting layers (plates), where Bean-Livingston barrier is effectively suppressed, but the flux flow out from the superconducting layers (plates) through the wide sides of the plates freely. The experimental proof of the barrier absence for the outflow of the magnetic flux on the border of the superconductor is received. Thus is shown, that the border (surface) of the type-II superconductor is the "semiconductor" for the magnetic flow: it lets the flux to flow out from the superconductor freely, but it interferes with the flux to flow into the superconductor.