EFFECT OF THE VORTEX CORE ON THE MAGNETIC-FIELD IN HARD SUPERCONDUCTORS

Using approximate analytical and numerical solutions of the convention al Ginzburg-Landau equations we calculate the small-angle neutron-scat tering cross section and the variance of the field distribution as mea sured by muon-spin rotation for superconductors with large Ginzburg-La ndau parameter kappa. Our results prove that a proper account of the f inite size of the vortex core is important, even at relatively low fie lds. This finding provides a natural explanation for the recently obse rved field dependence of the CeRu2 form factor and of the YBa2Cu3O6.95 penetration depth.