Orientational ordering of (formula presented) in the antiferromagnetic (formula presented) phase

The absence of superconductivity in the ammoniated alkali fulleride, (formula presented) and the transition to an antiferromagnetic (AF) Mott insulating ground state have been associated with the combined effects of crystal symmetry lowering and increased interfullerene separation. We find that the low-temperature orientational ordering motif of the (formula presented) units in the perdeuterated analog, (formula presented) correlates well with the three-dimensional AF structure proposed by NMR, which arises through alternate stacking of two-dimensional sheets of (formula presented) which order ferrorotationally (antiferromagnetically) along the (formula presented) and antiferrorotationally (ferromagnetically) along the (formula presented) directions.