Thermodynamic and Magnetic Properties of Ferric Chloride Intercalated Graphite

I report measurements of the low field static magnetization for stages 1, 2, 3, 4, 5, 6, and 8, and the specific heat for stages 2, 3, 4, 6, and 8 of ferric chloride intercalated graphite. The magnetization measurements are carried out in a magnetic field H_{ rm o} ~ 0.5G for all samples, and 0.03G < H _{rm o} < 5G for the stage 6 sample, in the temperature range 1K < T < 4.2K, using a squid magnetometer. The total magnetic moment M(T) shows an onset and a subsequent sharp rise in magnitude as the temperature is lowered below 2K for all stages studied but with a different magnitude for M_{s} = M(1K). The saturation magnetization M_ {s}(n) increases exponentially with stage n up to n = 6, and then decreases for higher stage. This behavior is similar to the behavior of the measured susceptibility maximum as a function of stage index. The derivative of M(T) with respect T is similar to chi_ {ac}(T). The stage 6 saturation magnetization seems to follow a power law in H_{ rm o}. Long relaxation times, tau_{M}, with interesting temperature dependence for 1K < T < 2K, are observed. The specific heat measurements are carried out using AC and DC calorimetry methods. The results show an anomaly in the specific heat around T ~ 1.8K in the stages studied. The total specific heat of a given state is analyzed in the light of its different contributions: (1) an electronic component with a linear dependence on T, (2) a lattice part proportional to T^2, indicative of a 2D phonon spectrum, and (3) a magnetic contribution. The stage dependence of the three different contributions to the specific heat is presented.