Giant Magnetoresistance in La_0.67Ca_0.33MnO₃/Alq₃/Co Sandwiched-Structure Organic Spin Valves

La_0.67Ca_0.33MnO₃/Alq₃/Co sandwiched-structure organic spin valves are fabricated by vacuum thermal evaporation method. A giant magnetoresistance (GMR) of 14% is observed at low temperature 100K. At 30K, the magnetoresistance can increase to 50%. The large GMR of the device is attributed to the high spin polarization and low conductivity of the La_0.67Ca_0.33MnO₃ contact. The magnetoresistance ΔR/R and the coercive field of the Co electrode depend strongly on temperature. The large high-field magnetoresistance reported on La_0.67Sr_0.33MnO₃/Alq₃/Co organic spin valves Nature 427 (2004) 821 is not observed in our La_0.67Ca_0.33MnO₃/Alq₂/Co organic spin valves.