Effects of the surface barriers on a critical state of a type-2 superconducting slab

The structure of the surface barrier in a critical state model is investigated theoretically. This barrier disappears when the external field B(sub O) approaches a superheating field B(sub s). An expression for B(sub s) is found for the case of the absence of the transport current. The metastable of the flux lines (FLs) can appear at B(sub O)=B', the supercooling field. The supercooling and the superheating fields are dependent on the applied field angle and on the self-field generated by a transport current flowing through the slab. The magnetic fields distribution at a critical current of a type II superconducting slab are predicted. The value of the critical current is dependent on the applied field angle.