ESR STUDY OF SOFT FERROMAGNETIC [TDAE]C-60 - A CRITICAL REINVESTIGATION

High-field ESR measurements of the soft ferromagnetic [TDAE]C-60 above T-c are presented. The ESR spectra are asymmetric already at elevated temperatures and reflect the symmetry of the unit cell. The data are critically put in the context to the results of other groups. It will be shown that in contrast to all previous publications the TDAE cations are an essential ingredient for the magnetism of this fullerene charge transfer complex. The spins in this complex are localized at higher temperatures, but are more and more delocalized by spin exchange interactions towards T-c. None of the results gives an indication that [TDAE]C-60 is an itinerant molecular ferromagnet. The exchange path includes the TDAE cations. That means, a strong exchange coupling between C-60 and TDAE prevails. Thus, no unplausible cancellation mechanism for the TDAE radical cation spins, as discussed extensively in the literature, must be considered.