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Organic spin valve devices with Co/Al2O3/8-hydroxyquinoline-aluminum (Alq3)/Co sandwich structure were fabricated and studied. Spin transport properties in the devices were investigated by measuring the current-voltage behavior and magnetoresistance (MR) at low temperature. With Al2O3 insertion, the relatively larger and positive MR ratio was observed with maximum value of around 19% at 5 K. The MR ratio was reduced with increasing temperature and finally disappeared above 80 K. In the case of devices without Al2O3 inserted layer, we have not observed MR at measured temperature. The role of Al2O3 inserted layer, spin transport mechanism, and the decrease of MR with increasing temperature in the organic spin valve were discussed.