Organic spintronics has been a field of growing interest due to the recent experimental work on half-metallic ferromagnetic colossal magnetoresistance (CMR) manganite/sexithienyl/CMR or CMR/Alq(3)/Co. The characteristic of carriers in sexithienyl-like organic polymers contacted with a CMR manganite is studied in the framework of a tight binding model. It is found that the formation of spin polarons can be energetically favorable than that of spinless bipolarons. Spin polarons can act as the main transport carriers in organic semiconductors. Effects of the interfacial coupling, spin splitting of the magnetic contact and lattice disorder with Coulomb interactions on the stability of polarons are discussed. (c) 2006 Elsevier B.V. All rights reserved.