ATOMIC-LEVEL ENGINEERING OF CUPRATES AND MANGANITES

Using ALL-MBE, we have engineered a novel, artificial (metastable) cup rate superconductor, BiSr2Ca7-xDyxCu8O19+y, in which only the central Ca layer is doped by Dy. This provides, within a single unit cell, the bottom superconducting electrode, an insulating barrier layer (only f ew A thick), and the top superconducting electrode, thus constituting an artificial intra-cell Josephson junction. In this way, we have fabr icated the first high-T-C tunnel (SIS) junctions. They exhibit signifi cant Josephson supercurrents and very sharp quasiparticle tunneling I- V characteristics. Next, single-crystal thin films of manganites grown by ALL-MBE have shown remarkable anisotropy of colossal magnetoresist ance (CMR). We have also fabricated lateral superlattices with alterna ting stripes (nano-wires) of La1-xCaxMnO3 and La1-xSrxMnO3, few tens o f nanometers wide. They show substantial in-plane anisotropy in transp ort properties, and a fivefold increase in low-field sensitivity. Our most recent results include successful growth of La1-xSrxMnO3 on top o f Bi2Sr2CaCu2O8, and vice versa.