Fullerene. Ergebnisse zur Druckabhaengikeit der Phasenuebergangstemperatur von Fulleriden

The determination of the pressure dependence of the phase transition temperature T_c of Fulleride superconductors (dt_c/dp) was shown to play a key role for the understanding of the superconducting state in this new class of materials. According to these experiments, electron phonon coupling is responsible for the Cooper-pair formation (BCS-theory valid). These findings mark the achievement of a main goal of this project, namely the characterization of the superconducting state of Fullerides. Since the ground state properties of BCS-type superconductors are well known further research about the basic understanding of superconductivity in Fullerides seems not to be worthwhile. New alkaline-fullerides have been synthesized (Ba_xC_6_0) of which Ba_4C_6_0 has been identified as superconducting and dT_c/dp was determined. T_c in fullerides was shown to depend on the size of the electronic density of states N, which in turn is a function of the intermolecular distance. Two of our findings are important with respect to the highest T_c to be expected in this new class of superconductors. Because of structural instabilities, T_c seems to be limited to T 35 K. In addition, hybridization of the electronic states of the intercalate with those of C_6_0 tends to lower T_c (alkaline fullerides). TDAE-C_6_0 is the molecular organic ferromagnetic material with the highest Curie-temperature known to date. In contrast to what was expected on the basis of pressure studies of T_C_u_r_i_e. (orig.)Available from TIB Hannover: F96B1379+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman