title: Metal-insulator and structural phase transition observed by ESR spectroscopy and x-ray diffraction in KC60.
abstract: We have performed electron spin resonance (ESR) spectroscopy and x-ray diffraction experiments at low temperature on KC60 single crystals. ESR data reveal the occurrence of a metal-insulator phase transition at about 50 K. In the same temperature range, we observe the stabilization of a superstructure which doubles the volume of the unit cell. We suggest that displacements of the K atoms and a modulation of the C60 charge may be involved in the mechanism of this phase transition. These results shed new light on the subtle interplay of structure, dimensionality, and electronic properties in the AC60 fullerides.
authors.affiliation: Centre de Recherche Paul Pascal (UPR CNRS 8641), Université Bordeaux-I, Av. du Dr Schweitzer, 33600 Pessac, France. coulon@crpp.u-bordeaux.fr
authors.forename: C
authors.initials: C
authors.lastname: Coulon
authors.forename: A
authors.initials: A
authors.lastname: Pénicaud
authors.forename: R
authors.initials: R
authors.lastname: Clérac
authors.forename: R
authors.initials: R
authors.lastname: Moret
authors.forename: P
authors.initials: P
authors.lastname: Launois
authors.forename: J
authors.initials: J
authors.lastname: Hone