The onset of vortex penetration into a hard superconductor induced by the rotation of an applied magnetic field

The onset of a vortex penetration into a hard isotropic superconductor afte r the rotation of an applied magnetic field (H) over right arrow is theoret ically studied. On the basis of the Gibbs formalism, macroscopic equations describing this process are derived. Different magnetic prehistories are co nsidered. It is shown that vortices entering into a sample are not parallel to the direction of (H) over right arrow. The angle between the vortices a nd (H) over right arrow can be unexpectedly large and reach pi/2. (C) 2000 Elsevier Science B.V. All rights reserved.