SUSCEPTIBILITY DISCONTINUITY IN SINGLE-CRYSTAL C60

Magnetization of a large single C60 crystal was measured as functions of applied field and temperature. At T = 260 K, a discontinuity in sus ceptibility was observed. The relative change in total moment is 1.2%, independent of applied field to within experimental accuracy. This di scontinuity is attributed to the change in the intramolecular geometry at the orientational order-disorder transition. This is the first exp erimental demonstration that the cooperative phase transition affects the magnetic susceptibility of a single molecule.