ESR study of the hydrogen-potassium-graphite ternary intercalation compounds

Abstract

The electronic properties of the stage-1 and -2 hydrogen-potassium-graphite ternary intercalation compounds (KH-GIC's) ${\mathrm{C}}_{4\mathrm{n}}$${\mathrm{KH}}_{\mathrm{x}}$ (n=1,2; x\ensuremath{\sim}0.8) were investigated by means of ESR measurements. The observed temperature dependence of the diffusion time is found to be associated not only with the conduction-electron spins but also with the localized spins. The behavior of the paramagnetic susceptibilities and the g values gives additional evidence for the presence of localized spins which interact with the conduction-electron spins. The KH-GIC's possess the ionic lattice of the donor intercalant with sandwich layers ${\mathrm{K}}^{+}$-${\mathrm{H}}^{\mathrm{\ensuremath{-}}}$-${\mathrm{K}}^{+}$, which are affected by the conduction electrons on the graphite layers. The composition ${\mathrm{C}}_{4\mathrm{n}}$${\mathrm{KH}}_{0.8}$ suggests hydrogen deficiency in the ${\mathrm{K}}^{+}$-${\mathrm{H}}^{\mathrm{\ensuremath{-}}}$-${\mathrm{K}}^{+}$ ionic intercalant, which gives defects in the intercalant. The presence of the localized spins is attributed to trapped electrons at the defects in the intercalants. The spin relaxation at high temperatures is explained with use of the Elliott mechanism. The exchange interactions between graphite \ensuremath{\pi} and alkali-metal s electrons and the large spin-orbit interaction of alkali-metal atoms play important roles in the relaxation process.