RB1C60 UNDER PRESSURE - AN NMR AND ESR STUDY

We report the results of magnetic measurements on the orthorhombic alk alimetal fulleride Rb1C60. Measurements of the NMR relaxation T-1 and ESR spin susceptibility under pressure (P less than or equal to 5 kbar ) provide clear evidence for the importance of electron correlations i n this phase at variance with superconducting phase 3 fullerides. We s how that spin fluctuations (ferromagnetic) persisting up to room tempe rature order antiferromagnetically at low temperature and give rise to long range order below 15 K. These results support the band structure calculation describing this polymerised phase by a three-dimensional model. The magnetic ground state is suppressed by a pressure exceeding approximate to 6 kbar and gives rise to a conducting phase at 12 kbar whose susceptibility is still possibly enhanced by magnetic fluctuati ons.