NMR EVIDENCE FOR 1D ANTIFERROMAGNETIC PROPERTIES IN CS1C60 AND RB1C60POLYMERS

We have performed C-13 NMR measurements on the three phases of A(1)C(6 0) (A = K,Rb,Cs) and alkali NMR in Cs1C60 (Cs-133) and Rb1C60 (Rb-87) We show that, for Rb1C60 and Cs1C60. strong antiferromagnetic (AF) flu ctuations persist up to room temperature, suggesting a one-dimensional character. However, K1C60 behaves as an ordinary three-dimensional me tal. NMR also reveals a magnetic transition at about 25 K in the Rb an d Cs polymers. Comparison of the Cs-133 and C-13 spectra supports the occurrence of a spin-flop AF phase. Simulations of the Cs-133 spectrum due to a distribution of dipolar fields are consistent with moments m similar or equal to 0.5 mu(B) ordered in AF chains.