Investigation of Spin-dependent transport properties and Spin-Spin interactions in a copper-phthalocyanine-cobalt nanocomposite system

We have fabricated a series of copper-phthalocyanine-cobalt (CuPc-Co) nanocomposites (compositional ratio of CuPc . Co=4 . 1), wherein Co nanoparticles were embedded within a CuPc matrix, in order to study the spin transport properties and to investigate spin-spin interactions between conducting spins and localized spins in the CuPc. Nonlinear characteristics of electric current, I-V(^2N-1), (V. bias voltage, N. order of cotunneling) were observed, where the fifth order co-tunneling was clarified. The order of the co-tunneling effect in CuPc-Co was almost equal to that in a rubrene-Co nanocomposite with almost the same diameter of the Co nanoparticles. We have not found clear evidence of spin-flip processes, as observed in other molecular systems, which may be attributed to the spin-coupling between localized spins in the CuPc and spins in Co.