Ferromagnetic Interaction in C60 Charge Transfer Complexes

Abstract

Abstract C60[TDAE] was the first and so far the only C60 CT complex which ex-hibits molecular ferromagnetism with a Curie temperature of about 16 K [1]. Despite extensively investigated a convincing access to the origin of the low temperature phase of this C60 CT complex is still missing. The 3 fold degeneracy of the C60 HOMO is lifted by a change of the C60 conformation, and we find a transition from a static low temperature Jahn-Teller distortion to a dynamic one at about 140 K. The excess electron is concentrated in a belt around the equator of the C60-. The distorted C60 molecules have a spin density distribution with an axial symmetry and are aligned along the crystallographic axes. This orientational ordering of the C60- molecules is the necessary precursor to a ferromagnetic spin glass type ordering in C60[TDAE] which was interpreted in terms of spin polarisation between C60- and TDAE+*by Yamaguchi et a1 [2].