High Resolution ¹³C NMR in K-Graphite Intercalation Compounds—C-Axis Charge Distribution

Abstract

High resolution ¹³C NMR has been observed in highly oriented crystals of pristine graphite and K-GIC’s. The NMR spectrum consists of several well resolved lines which can be assigned to the interior and bounding carbon layers. The ¹³C spin-lattice relaxation time T₁ shows the metallic characteristics, T₁T=constant between about 1.5 K and R.T. From T₁ of each resolved absorption line, the c-axis charge distribution was quantitatively determined for stage 3 and 6, which is strongly inhomogeneous. The obtained distribution was also supported by an analysis of the frequency shift of ¹³C NMR. In stage 1 it was suggested, from a comparison of T₁ with electronic specific heat, that the conduction electrons near the Fermi level spread over not only graphite layers but also interlayer space containing K-atoms.