The Route to Supercurrent Transparent Ferromagnetic Barriers in Superconducting Matrix.

A ferromagnetic barrier thinner than the coherence length in high-temperature superconductors is realized in the multilayers of YBa ₂ Cu ₃ O _7-δ and La _0.67 Ca _0.33 MnO ₃ . We used epitaxial growth of YBCO on ⟨110⟩ SrTiO ₃ substrates by pulsed laser deposition to prepare thin superconducting films with copper oxide planes oriented at an angle to the substrate surface. Subsequent deposition of LCMO and finally a second YBCO layer produces a superconductor/ferromagnet/superconductor trilayer containing an ultrathin ferromagnetic barrier with sophisticated geometry at which the long axis of coherence length ovoid of YBCO is pointing across the LCMO ferromagnetic layer. A detailed characterization of this structure is achieved using high-resolution electron microscopy.