Anomalous Phase Breaking in Dilute Fluorinated Graphene

Quantum interference induced weak localization and phase breaking measurements are sensitive tools to probe the existence of magnetic impurities in mesoscopic systems. In this work, we study the low-field magnetoresistance of dilute fluorinated graphene (DFG), with a fluorine adatom density of $\sim$~10$^{12}$/cm$^2$. In the DFG samples, the phase breaking time $\tau_\phi$ follows $T^{-1}$ at high temperature and saturates at $T$ $\sim$ 10 K. The former is consistent with electron-electron interaction. The latter cannot be accounted for by conventional theories based on sample size and charge inhomogeneity. We show the dependence of the saturated $\tau_\phi$ on the carrier density and fluorine coverage and discuss the effects of spin-flip scattering and localization in phase breaking. Our observations point to the presence of adatom induced local magnetic moments in dilute fluorinated graphene.