Proximity effect in oxide superconductor/ferromagnet films

We fabricated high-quality YBa₂Cu₃O_7-δ/La_2/3Ca_1/3 MnO₃ bilayers with 10 monolayers (∼ 12 nm) thin superconducting YBa₂Cu₃O_7-δ (YBCO)layers on top of ferromagnetic La_2/3Ca_1/3MnO₃ (LCMO) layers with a thickness varied between 5 and 35 monolayers (∼ 2–13 nm). We measured the transport properties of the YBCO layers and the magnetic properties of the LCMO layers as a function of the LCMO layer thickness. We observed a smooth linear increase of the Curie temperature T_C of the LCMO layer in the investigated thickness range, but a sudden strong decrease of the superconducting critical temperature T_c of the YBCO layer at a critical LCMO thickness of ∼ 12 nm. Since no dramatic change of the structural quality of the YBCO layers is observed we conclude that the increasing magnetization strength in the LCMO layer is responsible for the T_c suppression in the YBCO layer via proximity effect.