Ferromagnetic and half-metallic behaviors of fullerene-cobalt polymer chains

We present the results of first-principles calculations for polymers (C(60)-Co)(n) and (C(70)-Co)(n), which consist of alternating chains of fullerenes and cobalt. Both of them favor a ferromagnetic ground state. The latter one is a half-metal which will give rise to 100% spin polarization in the electronic transport, while the former is a semiconductor. Polymers (N@C(60)-Co)(n) and (N@C(70)-Co)(n), which encapsulate a nitrogen atom in each fullerene have magnetic moments four times larger than those without encapsulated nitrogen atoms. All these results can be explained in terms of pi(fullerene)-d(Co) and pi(fullerene)-p(N) hybridizations.