Conduction electron spin resonance in Rb/sub 1/C/sub /60 and Rb/sub 3/C/sub /60

Summary form only given. The conduction electron spin resonance of Rb/sub 3/C/sub /60 has been observed for the first time and the spin susceptibility found to be 12.4/sup */10/sup -4/ emu/mol in agreement with static measurements. The linewidth is anomalously large, 1300G at 30K, and we suggest that it is caused by large molecular disorder. The narrow ESR line formerly assigned to Rb/sub 3/C/sub /60 arises from the orthorombic phase ( stable below 360K) of Rb/sub 1/C/sub /60 which is a quasi 1D metal with a transition to a spin density wave state at 50K. The high temperature fcc phase ( above 360K) may be stabilized below 300K by quenching from 500K, is paramagnetic above 300K and transforms into a non-magnetic ground state between 300 and 250K.