Normal-state bubbles and lamellae in type-I superconductors

International audience; We report an extensive study of the formation of normal-state domains in type-I superconductors. Domain patterns are first considered theoretically. The magnetic interaction between domains is described in the framework of the ``current-loop'' model: the intermediate state is modeled by a set of loops of screening current encircling the domains and interacting as in the free space. This system is shown to be formally equivalent to a set of uniformly magnetized domains. An extension of the current-loop model is proposed to take into account the constraint of the magnetic shielding by the superconducting regions. We determine the free energy of a hexagonal array of cyl…