Origin of weak ferromagnetism in TDAE-C60

A mechanism leading to the coexistence of weak ferromagnetism and spin glass behavior in the weak organic ferromagnet TDAE-C60 is proposed. In view of the non-metallic character of TDAE-C60, the C60−-C60− intra-chain coupling along the c-axis as well as the inter-chain C60−-C60− assumed to be of antiferromagnetic nature. If the spin density on the TDAE+ ion is inhomogeneously distributed the TDAE+ mediated super-exchange leads to a ferromagnetic coupling between C60− ions on different chains. This leads to a Dzyaloshinsky-Moriya type coupling responsible for the spin-canting and a non-zero spontaneous magnetization. Other models like three dimensional ferromagnetic orbital ordering of Jahn-Teller distorted C60 molecules are discussed as well.