THE VORTEX CHAIN STATE IN PLANAR CRYSTALS OF YBA2CU3O7-DELTA

By minimising the Gibbs free energy for samples of a planar geometry a nisotropic London theory is used to predict the Abrikosov flux lattice for arbitrary field orientations. The results of this calculation are in close agreement to the Bitter pattern experiments of Gammel et al. [1], assuming an anisotropy ratio gamma = 5 and an inplane penetratio n depth lambda(ab) = 1 413 Angstrom. Moreover, once account has been t aken of the rotation of the vortex lattice as a function of the applie d field, we show that at low fields these results demonstrate the exis tence of the ''vortex-chain'' state, i.e. the inter-chain vortex separ ation scales as B-1, whereas the intra-chain vortex separation is fiel d independent [2].