Structure and physical properties of Cs 3 + α C 60 ( α = 0.0 – 1 . 0 ) under ambient and high pressures

The intermediate phases ${\mathrm{Cs}}_{3+\ensuremath{\alpha}}{\mathrm{C}}_{60}$ $(\ensuremath{\alpha}=0.0\char21{}1.0),$ have been prepared, and their structure and physical properties are studied by x-ray powder diffraction, Raman, ESR, electric conductivity, and ac susceptibility measurements under ambient and high pressures. The x-ray powder diffraction pattern of ${\mathrm{Cs}}_{3+\ensuremath{\alpha}}{\mathrm{C}}_{60}$ $(\ensuremath{\alpha}=0.0\char21{}1.0)$ can be indexed as a mixture of the body-centered-orthorhombic (bco) and cubic $(A15)$ phases. The $A15$ phase diminishes above 30 kbar. The broad ESR peak due to the conduction electron $(c\ensuremath{-}\mathrm{ESR})$ is observed only for the phases around $\ensuremath{\alpha}=0.0$ in ${\mathrm{Cs}}_{3+\ensuremath{\alpha}}{\mathrm{C}}_{60}.$ The resistivity of the ${\mathrm{Cs}}_{3+\ensuremath{\alpha}}{\mathrm{C}}_{60}$ $(\ensuremath{\alpha}\ensuremath{\ne}0)$ sample follows the granular metal theory and/or Sheng model even in the sample exhibiting a broad ESR peak. No superconducting transition is observed up to 10.6 kbar in ${\mathrm{Cs}}_{3+\ensuremath{\alpha}}{\mathrm{C}}_{60}$ $(\ensuremath{\alpha}\ensuremath{\ne}0).$ These results present that bco phase of ${\mathrm{Cs}}_{3+\ensuremath{\alpha}}{\mathrm{C}}_{60}$ $(\ensuremath{\alpha}=0)$ is a final candidate for a pressure-induced superconductor.