Orientational and Magnetic Ordering of Buckyballs in TDAE-C60

Science  21 Apr 1995:
Vol. 268, Issue 5209, pp. 400-402
DOI: 10.1126/science.268.5209.400


Spin ordering in the low-temperature magnetic phase is directly linked to the orientational ordering of C60 molecules in organically doped fullerene derivatives. Electron spin resonance and alternating current susceptometry measurements on tetrakis(dimethylamino)ethylene-C60 (TDAE-C60) (Curie temperature Tc = 16 kelvin) show a direct coupling between spin and merohedral degrees of freedom. This coupling was experimentally demonstrated by showing that ordering the spins in the magnetic phase imprints a merohedral order on the solid or, conversely, that merohedrally ordering the C60 molecules influences the spin order at low temperature. The merohedral disorder gives rise to a distribution of π-lectron exchange interactions between spins on neighboring C60 molecules, suggesting a microscopic origin for the observed spinglass behavior of the magnetic state.