Critical State Theory for Nonparallel Flux Line Lattices in Type-II Superconductors

Field penetration profiles in type-II superconductors with nonparallel vortex configurations are obtained by a proposed least action principle. We introduce a functional C[→H] which is minimized for the current density constrained by →J∈Δ(→H,→x), where Δ is a bounded set. Within the isotropic case |→J|≤Jc(H), the profiles →H(→x,t) are derived for an applied changing excitation. The model can reproduce the physical phenomena of flux transport and consumption, and the magnetization collapse in crossed field measurements.