Orientation dependent magnetic interaction in TDAE-C60, where TDAE is tetrakis(dimethylamino)ethylene

We have calculated effective magnetic interaction Jeff between the nearest neighbor (N.N.) C60− molecules in TDAE-C60, where TDAE is tetrakis(dimethylamino)ethylene with the dimer model. We found that Jeff is strongly dependent on the Euler angle and hence on orientation of the two molecules. The orientational dependence is a consequence of both the frontier orbital control and non-uniformity of spatial extension of the singly occupied molecular orbital (SOMO). The orientational dependence in this system could result in random distribution of magnetic interaction, when there is rotational randomness of C60− molecules in that compound as has been suggested by recent experiments.