S=1/2 antiferromagnetic finite chains effectively isolated by frustration: ${\mathrm{CuCl}}_2$-intercalated graphite

We have measured the static susceptibility of nominal stage-2 ${\mathrm{CuCl}}_2$-graphite intercalation compounds prepared from four different host graphites (highly oriented pyrolitic graphite, natural graphite crystals, and graphite fibers heat treated at 2500 and 3290 °C). The susceptibility and its anisotropy both contain a 1/T component which is shown to be due to finite-size effects and which, when removed from the data, reveals a bulklike behavior that closely corresponds to the pristine behavior for T>50 K. The behavior at lower temperatures is more complicated but is entirely consistent with an intercalate-island diameter of $d_{\mathrm{isl}\mathrm{\simeq }}$100 Å, leading to a distribution of finite isolated quasi-Heisenberg antiferromagnetic chains of S=1/2 ${\mathrm{Cu}}^{2+}$ ions.