Orientational and Magnetic Ordering of Buckyballs in TDAE-C 60

Abstract

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 T_c = 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.