Alkali spin-orbit interactions and the width of the conduction-electron spin resonance in superconducting alkali-metal fullerides

It is shown that conduction-electron spin relaxation in the superconducting alkali-metal fullerides is due to spin-orbit interactions within the alkali ion p orbitals that are admired into the C-60-based conduction band states when these band states are orthogonalized to the alkali orbitals, as required to satisfy the Pauli exclusion principle. The calculated electron-spin-resonance (ESR) linewidths support experimental findings that the broader of the two ESR lines often observed in these compounds is due to conduction electrons. The anomalous increase in the width of this line with decreasing temperature is due to strong scattering in a narrow conduction band.