Физика Низких Температур: Том 27, Выпуск 9-10 (Сентябрь 2001), c. 980-990 ( к оглавлению , назад )
Geometric edge barrier in the Shubnikov phase of type II superconductors
Ernst Helmut Brandt
Max-Planck-Institut für Metallforschung, D-70506 Stuttgart, Germany and Institute for Superconducting and Electronic Materials, University of Wollongong, NSW 2522 Australia
Received April 25, 2001
In type II superconductors the magnetic response can be irreversible due to two different reasons: vortex pinning and barriers for flux penetration. Even without bulk pinning and in absence of a microscopic Bean-Livingston surface barrier for vortex penetration, superconductors of nonellipsoidal
shape can exhibit a large geometric barrier for flux penetration. This edge barrier and the resulting irreversible magnetization loops and flux-density profiles are computed from continuum electrodynamics
for superconductor strips and disks with constant thickness, both without and with bulk pinning. Expressions are given for the field of first flux entry Hen and for the reversibility field Hrev above which the pin-free magnetization becomes reversible. Both fields are proportional to the lower critical field Hc1 but else depend only on the specimen shape. These results for rectangular cross section are compared with the well known reversible magnetic behavior of ideal ellipsoids.