Ferromagnetic versus molecular ordering in C60 charge transfer complexes

[TDAE]C60 (TDAE, tetrakis(dimethylamino)ethylene) was the first and is so far the only C60 charge transfer complex, which exhibits molecular ferromagnetism with a Curie temperature of about 16 K. Though extensively studied a convincing access to the origin of the low-temperature phase is still missing. Three mechanisms for the ferromagnetism will be compared: the classical Heisenberg ferromagnet, configuration interaction and spin polarization. The role of molecular ordering and of the Jahn-Teller distortion of C60 will be discussed.