Electron-spin-resonance study of fluorine-intercalated graphite fibers

We have measured the electron-spin-resonance (ESR) signal of fluorine-intercalated grpahite fibers with fluorine concentrations ranging from ${\mathrm{C}}_{6.6}$F to ${\mathrm{C}}_{3.1}$F. Previous transport measurements have shown that ${\mathrm{C}}_{\mathit{x}}$F fibers are two-dimensional materials that behave as disordered metals for dilute fluorine concentrations and as insulators beyond an approximate threshold ${\mathrm{C}}_{3.6}$F. In this paper, we report the temperature dependence (10–300 K) of the susceptibility, g factor, and ESR linewidth of the ${\mathrm{C}}_{\mathit{x}}$F fibers. We also measured the spin-lattice relaxation time of the fibers at 10 K from the power dependence of the ESR signal. The results are explained by the presence of both localized and conduction spins, and by the shift from an ordered 2D metal to a disordered 2D inhomogeneous insulator as the fluorine concentration is increased.