Superconducting Transition Temperature in YBa2 Cu4O8/La2/3Ca1/3 MnO3/YBa2Cu4O8 Heterostructure

YBa2Cu4O8/La2/3 Ca1/3 MnO3/YBa2Cu4O8 (Y-124/LCMO/Y-124) heterostructure was prepared by facing-target sputtering technique. The oscillatory superconducting transition temperature was observed when the thickness of LCMO dL is larger than critical thickness dLCR. The metal-insulator transition temperature can only be detected at dLCR. The dependence on the spacer layer in LCMO/Y-124 systems suggests strongly the interplay of ferromagnetic and superconducting couplings.