J. Phys. I France
Volume 6, Numéro 12, December 1996
Page(s) 2181 - 2190
DOI: 10.1051/jp1:1996214
J. Phys. I France 6 (1996) 2181-2190

Rb $\mathsf{_1}$C $\mathsf{_{60}}$ under Pressure: an NMR and ESR Study

P. Auban-Senzier1, D. Jérome1, F. Rachdi2, G. Baumgartner3 and L. Forro3

1  Laboratoire de Physique des Solides associé au CNRS, Université Paris-Sud, 91405 Orsay Cedex, France
2  GDPC, Université Montpellier II, Place E. Bataillon, 34060 Montpellier, France
3  Ecole Polytechnique Fédérale de Lausanne, 1015, Lausanne, Suisse

(Received 29 July 1996, received in final form and accepted 30 August 1996)

We report the results of magnetic measurements on the orthorhombic alkali-metal fulleride Rb 1C 60. Measurements of the NMR relaxation T1 and ESR spin susceptibility under pressure ( $P\leq 5$ kbar) provide clear evidence for the importance of electron correlations in this phase at variance with superconducting phase 3 fullerides. We show that spin fluctuations (ferromagnetic) persisting up to room temperature 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  $\approx 6$ kbar and gives rise to a conducting phase at 12 kbar whose susceptibility is still possibly enhanced by magnetic fluctuations.

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