K3+δC84. Higher Fullerene Analogues of the A3C60 Superconductors

Abstract

Face-centered cubic phases of both the D2 and D2d isomers of the C84 anion with band fillings close to those of the A3C60 superconductors are prepared by a two-step reaction involving saturated K8+xC84 phases as intermediates. Rietveld refinement shows that the structures are more disordered than those of K8+xC84, with incomplete occupancy of multiple cation sites and the presence of two anion orientations, while both temperature-dependent powder diffraction and EPR demonstrate the monophasic nature of the reaction products. The temperature-independent magnetic susceptibilities and line width variation in EPR indicate that these phases have finite densities of states at the Fermi level for both C84 majority isomers, unlike the previously prepared saturated phases, but dc magnetization measurements indicate the absence of superconductivity above 5 K.