Bistability effects in solvent-including metallofullerene crystals

Magnetic bistability has been discovered in the low temperature properties of the solvent-including metallofullerene single crystals Ln@C-82(CS2)(1.5) (Ln = La, Ce). In these insulating compounds a single paramagnetic spin is localized on the fullerene cage at room temperature. Control of the coolin g rate through an observed transition at similar to 150K results in either quenching or persistence of the fullerene spin and antiferromagnetic intera ctions at low temperatures. This bistability seems to be a common phenomena in metallofullerenes. This paper presents a low temperature x-ray diffract ion investigation of the crystals, however no evidence of a structural phas e transition has been found that could have been the origin of the bistabil ity.