Magnetoresistance effects on La0.67Ca0.33MnO3/YBa2Cu3Oy/Ni trilayers

La0.67Ca0.33MnO3 (LCMO)/YBa2Cu3Oy (YBCO)/Ni trilayers were fabricated with varying thickness of the mid-superconducting YBCO layer. Two different deposition systems were used to avoid oxidation of the magnetic metal Ni and contamination of the deposition systems. Transport properties show that the temperature dependence of resistance goes from a metallic-to-metal-insulator transition (manganite-like behavior) to a superconducting behavior (M-M-S) with increase of the thickness of the YBCO layer. The magnetoresistance (MR) ratio is very small in comparison with LCMO/YBCO bilayers at low temperature. Such phenomenon may depend on the charge transfer and the magnetic spin interaction between the bottom and cap magnetic layers.