Formation of submicron-thick oxide barrier for reducing AC loss in multifilamentary Bi2223 tapes

Barrier surrounding oxide superconducting core is effective in reducing AC loss of the multifilamentary tape. Metallic magnesium was chosen as its precursor material. Through the ordinary deformation process to fabricate the tape, the magnesium layer was easily thinned up to sub-micron. By the successive oxidation treatment, the barrier became a stable MgO layer. Usefulness of ductile material has been demonstrated to produce ultra-thin barrier.