Approaching magnetic ordering in graphene materials by FeCl₃ intercalation

We show the successful intercalation of large area (1 cm$^2$) epitaxial few-layer graphene grown on 4H-SiC with FeCl$_3$. Upon intercalation the resistivity of this system drops from an average value of $\approx 200 \ \Omega/sq$ to $\approx 16 \ \Omega/sq$ at room temperature. The magneto-conductance shows a weak localization feature with a temperature dependence typical of graphene Dirac fermions demonstrating the decoupling into parallel hole gases of each carbon layer composing the FeCl$_3$ intercalated structure. The phase coherence length ($\approx 1.2 \mu$m at 280 mK) decreases rapidly only for temperatures higher than the 2-D magnetic ordering in the intercalant layer while it tends to saturate for temperatures lower than the antiferromagnetic ordering between the planes of FeCl$_3$ molecules providing the first evidence for magnetic ordering in the extreme two-dimensional limit of graphene.